LABORATORY  MANUAL 
of  ORGANIC  CHEMISTRY 


BY 


HARRY  L.  FISHER,  Ph.D. 

Instructor  In  Organic  Chemistry,  Columbia  University 


NEW   YORK 

JOHN    WILEY   &    SONS,    INC, 

LONDON:   CHAPMAN  &  HALL,   LIMITED 
1920 


/x' 


Copyright,  1920 

BY 
HARRY  L.  FISHER 


4/20 


BRAUNWOHTH  &  00. 

BOOK  MANUFACTURERt 

BROOKLYN.  N.  V. 


PREFACE 


THIS  book  is  the  outgrowth  of  almost  ten  years  of  intensive 
laboratory  teaching.  Practically  all  the  laboratory  experi- 
ments, in  mimeograph  form,  have  been  in  the  hands  of  three 
different  classes  of  students,  day,  night,  and  summer,  each  year 
for  over  five  years,  and  during  this  time  have  been  repeatedly 
corrected.  As  our  classes  grew  we  found  it  necessary  to  keep 
to  a  definite  list  of  experiments  and  all  our  attention  was  devoted 
to  these.  In  order  to  bridge  the  gap  between  the  particular  reac- 
tion studied  and  allied  reactions,  many  questions  were  added. 
These  questions  have  been  made  the  basis  of  laboratory  quizzing 
and  are  meant  primarily  for  the  student  to  use  for  his  own  ad- 
vancement in  the  subject  to  aid  him  to  become  his  own  teacher. 
A  portion  of  the  questions  are  on  the  practical  work  in  the 
laboratory,  that  is,  on  the  methods  of  handling  apparatus,  etc. 
Many  of  them  will  appear  to  be  perfectly  obvious.  They  are, 
nevertheless,  put  in  since  it  has  been  noticed  that  it  is  the  most 
obvious  point  which  is  most  often  overlooked. 

The  experiments  are,  in  general,  the  usual  ones  found  in 
laboratory  manuals,  changed  of  course  in  accordance  with  our 
experience,  and  they  were  chosen  for  their  teaching  value  and 
for  the  good  all-round  practical  manipulation  involved.  There 
are  only  a  few  innovations.  Menthone  and  menthone  oxime 
illustrate  typical  reactions  even  though  their  formulas  may  seem 
large  to  the  beginner.  Glycocoll  is  prepared  by  hydrolysis, 
thus  linking  up  the  chemistry  of  the  proteins  with  that  of 
simpler  compounds.  Limonene  dihydrochloride  has  tremendous 
teaching  value,  and  the  synthesis  of  camphor  from  pinene  gives 
an  opportunity  for  select  work  in  an  enticing  field.  The  methods 
described  give  good  yields  in  most  cases,  but  the  yield  was 
not  the  prime  reason  for  choosing  any  experiment. 

It  will  be  noticed  that  there  are  no  directions  for  preparing 

iii 

416849 


iv  PREFACE 

such  substances  as  acetacetic  ester,  malonic  ester,  etc.  These 
can  advantageously  be  given  in  connection  with  special  advanced 
synthetic  work,  for  example,  malonic  ester  can  be  prepared  as 
the  starting-point  in  the  synthesis  of  veronal  (barbital),  acet- 
acetic ester  and  also  phenyl  hydrazine  in  the  preparation  of 
antipyrine,  anthraniiic  acid  for  methyl  anthranilate  or  indigo, 
ethylene  chlorhydrin  for  novocaine  (procaine),  pyruvic  acid 
for  atophan,  etc. 

In  the  large  classes  of  to-day  the  beginning  student  does  not 
any  longer  have  the  opportunity  of  "  rubbing  elbows  "  with  the 
older  men  and  learning  from  such  contact  many  of  the  little 
things  about  laboratory  manipulation  which  aid  materially  in  the 
successful  outcome  of  an  experiment.  For  this  reason,  the 
first  experiments  in  this  book  are  written  up  in  considerable  detail 
with  the  hope  that  after  the  student  has  learned  how  to  set  up 
his  apparatus  in  the  correct  way,  he  will  thereafter  follow  this 
practice.  For  the  most  part  this  hope  has  been  realized  in  this 
laboratory.  All  operations  are  described  where  they  are  first 
used,  in  the  order  of  the  experiments,  and  afterwards  their  use 
only  is  mentioned,  sometimes  being  cross-referenced,  but  always 
fully  indexed.  Special  discussions  are  included  only  where  it  is 
believed  the  material  cannot  be  found  in  the  ordinary  books  which 
the  student  has  at  his  disposal. 

It  is  assumed  that  before  beginning  organic  laboratory 
work  students  have  been  prepared  with  a  long  course  in  general 
chemistry  and  a  short  course  in  qualitative  analysis. 

A  shortened  organic  course  is  mentioned  below  which  has  been 
designed  especially  for  pre-medical  students.  A  good  grounding 
in  organic  chemistry  is,  however,  absolutely  essential  for  the 
study  of  medicine,  and  the  long  course  should  be  taken  whenever 
possible.  A  student  gets  much  more  out  of  his  work  when  he 
prepares  certain  compounds  and  has  time  to  study  their  char- 
acteristics and  think  over  his  work,  than  when  he  goes  through  a 
very  great  number  of  test-tube  reactions  which  superficially  are 
very  much  alike  and  therefore  the  more  easily  forgotten. 

The  long  course  consists  of  two  afternoons  a  week  for  two 
semesters,  and  comprises  for  the  first  semester,  experiments 


PREFACE  V 

Nos.  1-7,  9-15,  17-23,  and  for  the  second  semester,  experiments 
Nos.  24-29  (i),  30-46,  48-49?  5J-53>  56>  58,  65,  66.  These  are 
arranged  in  the  order  of  discussion  found  in  Stoddard's  "  Intro- 
duction to  Organic  Chemistry."  The  short  course  consists  of 
two  afternoons  for  one  semester,  and  comprises  experiments 
Nos.  i,  2,  3,  4,  28,  5,  10,  6,  24,  12,  25,  29  (i),  16,  19,  22,  30,  8,  9, 
26,  27,  34,  37,  33,  38,  43,  45,  46,  51,  53,  49,  13  (optional),  in  the 
order  given.  This  different  order  is  in  accordance  with  the 
discussion  in  Moore's  "  Outlines  of  Organic  Chemistry."  Since 
the  order  of  both  courses  is  not  the  same,  some  of  the  experiments 
in  the  long  course  which  also  occur  early  in  the  short  course, 
have  been  written  up  in  greater  detail  than  would  ordinarily 
be  necessary  from  their  position  in  the  list.  A  list  of  apparatus 
furnished  to  each  student  and  lists  of  the  chemicals  used  in  each 
course  will  be  found  on  pages  312-323.  In  our  laboratory  each 
student  receives  his  complete  set  of  chemicals  and  apparatus 
for  the  semester  when  he  starts  work,  and  keeps  them  in  his  desk. 

Each  desk  in  the  organic  laboratory  at  Columbia  University 
is  equipped  with  gas  (2),  air  blast,  water  (2  outlets  including  one 
which  can  be  used  for  suction  pump),  steam  cup,  steam  outlet 
for  steam  distillation,  etc.,  draft  pipe  (downward),  and  electric 
fixture  for  extra  light  and  with  a  2o-ampere  connection.  It 
is  expected  that  in  addition  a  special  hot-plate  will  soon  be 
installed  having  a  steam  pipe  cast  in  it  and  also  having  another 
pipe  cast  in  it  which  can  be  connected  with  the  air  blast  to 
give  hot  air  when  desired.  At  the  adjacent  sink  is  a  goose-neck 
outlet  for  water  and  another  one  with  a  steam  mixer  attached 
for  producing  water  of  any  desired  temperature.  The  desks, 
phich  are  6  feet  long,  contain  the  Fales  type  of  cupboards,  and 
are  arranged  for  two  students  to  work  on  alternate  afternoons. 
There  are  no  shelves  or  racks  between  the  desks  and  on  this 
account  the  room  is  light  and  it  is  possible  to  look  across  the  entire 
laboratory  at  any  time.  The  room  is  of  course  equipped  with 
fire  extinguishers,  bottles  of  dry  sodium  bicarbonate  for  burning 
oil,  and  blankets,  at  each  end  of  every  aisle,  and  three  needle 
shower-baths  in  case  one's  clothing  catches  fire. 

A  book  is  never  a  thing  by  itself.     It  is  always  a  growth  and 


VI  PREFACE 

many  factors  and  influences  from  other  workers  contribute 
largely  in  the  making  of  it.  The  author  is  very  glad  to  make 
acknowledgment  for  assistance  of  various  kinds  to  such  works 
as  the  following:  Barnett,  "The  Preparation  of  Organic  Com- 
pounds"; J.  B.  Cohen,  "  Practical  Methods  of  Organic  Chem- 
istry"; E.  Fischer,  "  Introduction  to  the  Preparation  of  Organic 
Compounds";  Gattermann,  "  Practical  Methods  of  Organic 
Chemistry";  Henle,  "  Anleitung  fur  das  organisch  praparative 
Praktikum";  Holleman,  "Laboratory  Manual  of  Organic 
Chemistry  for  Beginners  ";  L.  W.  Jones,  "  Laboratory  Outline 
of  Organic  Chemistry";  F.  J.  Moore,  "  Experiments  in  Organic 
Chemistry  ";  J.  F.  Norris,  "  Experimental  Organic  Chemistry  "; 
W.  A.  Noyes,  "  Organic  Chemistry  for  the  Laboratory  ";  Sud- 
borough  and  James,  "  Practical  Organic  Chemistry  ";  and  Ull- 
mann,  "  Organisch-chemisches  Praktikum."  Special  references 
are  given  here  and  there  largely  to  induce  students  to  get  ac- 
quainted with  articles  in  the  journal  literature  and  thus  to 
stimulate  them  toward  acquiring  a  good  scientific  attitude  toward 
chemistry. 

I  wish  to  make  most  generous  acknowledgment  to  my  friend 
and  colleague,  Professor  John  M.  Nelson.  The  work  herein  set 
forth  was  begun  with  him  and  grew  under  his  constant  sympa- 
thetic support  and  kindly  guidance.  His  sound  advice  and 
valuable  suggestions  call  for  my  most  cordial  thanks. 

I  am  also  indebted  to  Professor  Thos.  B.  Freas  and  his  asso- 
ciates of  the  stock  room  for  many  favors  and  to  Mr.  S.  J.  Ballard, 
who  made  many  of  the  drawings  and  prepared  all  for  the  pub- 
lishers. My  sincere  thanks  are  also  given  to  Dr.  George 
Scatchard  and  Mr.  William  E.  Morgan,  and  to  many  students 
whose  friendly  advice  and  helpful  co-operation  has  been  of  the 
greatest  assistance. 

A  special  foreword  concerning  organic  combustions  which 
constitutes  the  subject  of  the  second  part  of  this  work  will  be 
found  just  preceding  that  part. 

HARRY  L.  FISHER 

COLUMBIA  UNIVERSITY, 
June,  1919. 


CONTENTS 


PART  I 
LABORATORY  EXPERIMENTS 

EXPT.  NO.  PAGE 

GENERAL  NOTES  AND  SUGGESTIONS i 

IN  CASE  OF  ACCIDENT  OR  FIRE 6 

*i.  DETERMINATION  or  THE  BOILING-POINT  AND  STANDARDIZA- 
TION OF  THE  THERMOMETER  IN  THE  ORDINARY  DISTILLA- 
TION APPARATUS 7 

*2.  FRACTIONAL  DISTILLATION;  FRACTIONATION  OF  A  MIXTURE 

OF  ETHYL  ALCOHOL  AND  WATER 22 

*3.  ABSOLUTE  ALCOHOL 26 

*4.  TESTS  FOR  CARBON  AND  HYDROGEN  IN  ORGANIC  COMPOUNDS  30 
*5.  METHANE  FROM  CHLOROFORM  AND  CHEMICAL  PROPERTIES 

OF  PARAFFIN  HYDROCARBONS 31 

*6.  PREPARATION  OF  ETHYL  IODIDE  FROM  ETHYL  ALCOHOL.  ...  35 

7.  PREPARATION  OF  ETHYLENE  AND  ETHYLENE  DIBROMIDE.  .  40 

*8.  ETHYLENE 48 

*g.  ACETYLENE — 

(i.)  From  Calcium  Carbide 50 

(2.)  From  Ethylene  Dibromide 52 

*io.  ALCOHOLS,  REACTIONS  OF 54 

ii.  THE    IDENTIFICATION    OF    AN    ALCOHOL — THE    METHYL 

ESTER  OF  3.5-DiNiTROBENZOic  ACID 55 

*i2.  DETERMINATION  OF  THE  MELTING-POINT 58 

*i3.  PREPARATION   OF   DIMETHYL-ETHYL-CARBINOL   (GrignarcTs 

Reaction) 69 

14.  PREPARATION  OF  METHYL-PHENYL-CARBINOL 73 

15.  DISTILLATION  in  vacua  OR  UNDER  DIMINISHED  PRESSURE.  .  76 

*  These  experiments  constitute  the  short  course,  see  p.  v. 
vii 


viii  CONTENTS 

EXPT.  NO.  PAGE 

*l6.   ACETALDEHYDE  (Solution) 83 

17.  PREPARATION  OF  ACETALDEHYDE  AMMONIA 85 

18.  ACETALDEHYDE  FROM  ALDEHYDE  AMMONIA go 

*ig.  TESTS  FOR  ALDEHYDES 91 

20.  METHYLAL.    HYDROLYSIS  OF  METHYLENE  DIETHERS 94 

21.  FORMALDEHYDE:    TEST  FOR  FORMALDEHYDE,  AND  PREPA- 

RATION OF  HEXAMETHYLENETETRAMINE 96 

*22.  ACETONE 98 

23.  PREPARATION  OF  J-MENTHONE  AND  /-MENTHONE  OXIME.  . .  99 

*24.  PREPARATION  OF  ACETYL  CHLORIDE 102 

*25.  PREPARATION  OF  ETHYL  ACETATE 106 

*26.  HYDROLYSIS  (SAPONIFICATION)  OF  BUTTER 108 

*2y.  LECITHIN  FROM  EGG- YOLK no 

*28.  DETECTION  OF  NITROGEN,  SULFUR,  THE  HALOGENS,  AND 

PHOSPHORUS  IN  AN  ORGANIC  COMPOUND 112 

*29.  PREPARATION  OF  ACETAMIDE — 

(1)  From  Ammonium  Acetate  and  Glacial  Acetic  Acid.  .  115 

(2)  From  Ammonium  Acetate  in  a  Sealed  Tube 117 

*3o.  METHYL  AMINE 120 

31.  ETHYL  ISOCYANATE 122 

32.  METHYL  MUSTARD  OIL 1 23 

*33.  PREPARATION  OF  GLYCOCOLL  FROM  HIPPURIC  ACID.    PURI- 
FICATION OF  AN  AMINO  ACID 124 

*34.  HYDROLYSIS  OF  SUCROSE  (CANE  SUGAR)  AND  PREPARATION 

OF  PHENYLGLUCOSAZONE 127 

35.  PENTOSES.    FURFURAL  TEST 132 

36.  PREPARATION  OF  Mucic  ACID 134 

*37.  CELLULOSE  ACETATE 137 

*38.  BENZENE:  CHEMICAL  PROPERTIES 138 

39.  PREPARATION  OF  ETHYL  BENZENE  (Fittig's  Reaction) ....  141 

40.  PREPARATION  OF  DIPHENYLMETHANE  (Friedel-Crafts'  Re- 

action)    144 

41.  TRIPHENYLMETHYL 147 

42.  PREPARATION  OF  BROMBENZENE 149 

*43.  PREPARATION  OF  BENZENE  SULFONIC  ACID,  SODIUM  SALT.  .  152 

44.  PREPARATION  OF  NITROBENZENE 154 

*45.  PREPARATION  OF  ANILINE 157 

*46.  PREPARATION  OF  ACET-O-TOLUIDIDE 164 

47.  PREPARATION  OF  SULFANILIC  ACID 167 


CONTENTS  ix 

EXPT.  NO.  PAGE 

48.  BENZIDINE  REARRANGEMENT 169 

*49.  DYES:  PREPARATION  OF  METHYL  ORANGE 170 

PHENOLPHTHALEIN 171 

FLUORESCEIN 171 

CRYSTAL  VIOLET 17! 

50.  PREPARATION  OF  CRYSTAL  VIOLET 175 

*5i.  PREPARATION  OF  PHENOL,  AND  REACTIONS  OF  PHENOLS.  . .  177 

52.  PREPARATION  OF  ANISOLE 180 

*53.  BENZALDEHYDE 182 

54.  PREPARATION  OF  HYDROCINNAMIC  ACID. 184 

55.  PREPARATION  OF  ^-TOLUNITRILE 187 

56.  PREPARATION  OF  ACETANTHRANILIC  ACID 189 

57.  PREPARATION  OF  METHYL  SALICYLATE 191 

58.  TANNIN '. 193 

59.  PREPARATION  OF  LIMONENE  DIHYDROCHLORIDE 195 

60.  CAMPHOR  SYNTHESIS:  PINENE  HYDROCHLORIDE 198 

61.  CAMPHENE 202 

62.  ISOBORNYL  ACETATE 205 

63.  ISOBORNEOL 206 

64.  CAMPHOR 208 

65.  PREPARATION  OF  ANTHRAQUINONE 210 

66.  PYRIDLNE  AND  QUINOLINE 213 

PART  II 
ORGANIC  COMBUSTIONS 

DIVISION  A 
The  Determination  of  Carbon  and  Hydrogen 

PAGE 

I.  HISTORICAL  INTRODUCTION 217 

II.  LIST  OF  APPARATUS  AND  CHEMICALS 2  23 

III.  TOPICAL  OUTLINE  OF  GENERAL  METHOD  OF  PROCEDURE.  .   224 

IV.  THE  APPARATUS  AND  How  TO  PUT  IT  TOGETHER,  WITH 

NOTES  ON  MANIPULATION 225 

The  apparatus  is  arranged  in  the  following  order  and 
is  discussed  in  this  same  order : 

i.  Tank  of  Compressed  Oxygen  with  Stand  and  Pressure 
Gauges , , 225 


X  CONTENTS 

PAGE 

2.  Bubble  Counter 227 

3.  Gas  Purifying  Apparatus,  including  the  Pre-heater.  ...  228 

4.  a.  The  Electric  Combustion  Furnace 230 

b.  The  Combustion  Tube  and  How  to  Fill  It 231 

5.  Absorption  Train 236 

a.  First  Absorption  Bottle:  for  Water 238 

b.  Second  Absorption  Bottle:  for  Carbon  Dioxide 243 

c.  Guard   Tube    and    Bottle    of    Palladious    Chloride 
Solution 245 

V.  METHOD  OF  RUNNING  BLANK  DETERMINATIONS 246 

VI.  WEIGHING  THE  ABSORPTION  BOTTLES 248 

VII.  WEIGHING  THE  SUBSTANCE 250 

VIII.  THE  COMBUSTION  PROPER 253 

IX.  CALCULATIONS,  AND  DISCUSSION  or  RESULTS 257 

X.  SOME  COMMON  ERRORS  AND  How  TO  AVOID  THEM 261 

XI.  COMBUSTION    OF    SUBSTANCES    CONTAINING    NITROGEN, 

SULFUR,  HALOGENS,  PHOSPHORUS,  SODIUM,  ETC 265 

XII.  COMBUSTION  OF  LIQUIDS,  GASES,  AND  EXPLOSIVE  SUB- 
STANCES   , 267 

DIVISION  B 
The  Determination  of  Nitrogen 

I.  HISTORICAL  INTRODUCTION 269 

II.  LIST  OF  APPARATUS  AND  CHEMICALS 271 

III.  TOPICAL  OUTLINE  OF  GENERAL  METHOD  OF  PROCEDURE.  .  273 

IV.  THE  APPARATUS  AND  How  TO  PUT  IT  TOGETHER,  WITH 

NOTES  ON  MANIPULATION 275 

1.  The  Carbon  Dioxide  Generator 275 

2.  The  Manometer,  accompanying  Stop-cocks,  U-tube, 

etc 281 

3.  The  Electric  Combustion  Furnace 283 

4.  The  Combustion  Tube  and  How  to  Fill  It 284 

5.  The  Azotometer  (Nitrometer) 285 

V.    THE  FINAL  PREPARATION  OF  THE  CUPRIC  OXIDE 288 

VI.  WEIGHING  THE  SUBSTANCE 292 

VII.  THE  COMBUSTION  PROPER 293 

VIII.  CALCULATIONS,  AND  DISCUSSION  OF  RESULTS 300 

TABLES  FOR  NITROGEN 303 

TABLE  OF  LOGARITHMS 308 


PART  I 

LABORATORY  EXPERIMENTS 


LABORATORY    MANUAL    OF    ORGANIC 
CHEMISTRY 


GENERAL  NOTES  AND  SUGGESTIONS 

Each  preparation,  if  a  liquid,  is  placed  in  a  square  15  cc. 
glass-stoppered  bottle,1  and,  if  a  solid,  in  a  20  cc.  round  wide- 
mouthed  bottle,1  and  neatly  labeled  with  the  name  of  the 
substance,  the  corrected  boiling-point  or  melting-point,  as  found 
by  you,  the  yield  of  pure  substance  (always  in  grams,  to  the 
first  decimal  place,  as  originally  obtained  even  though  some 
material  may  have  been  used  for  special  experiments),  and  the 
name  of  the  student,  for  example: 

Ethylene  dibromide 

B.  P.  131°  cor. 

Yield,  20.2  grams 

JOHN  SMITH 

The  yield  is  the  amount  of  pure  product  actually  obtained. 
The  "theoretical  yield"  is  the  amount  which  would  be  obtained 
if  the  reaction  went  entirely  to  the  right  according  to  the  ordi- 
nary equation,  in  other  words,  if  the  starting  material  was 
entirely  converted  into  the  product  desired. 

The  yield  given  in  the  experiments  is  the  amount  usually 
obtained  by  following  out  the  directions  carefully.  It  is  not 
the  theoretical  yield. 

1  Practically  all  the  preparations  will  give  amounts  that  will  be  contained  by 
bottles  of  these  sizes.  Acetaldehyde  ammonia  and  acet-o-toluidide  will  be  found 
too  bulky,  but  it  is  expected  that  only  a  sample  of  these  will  be  handed  in  for 
inspection,  the  remainder  being  used  for  preparing  another  substance. 


2  LABORATORY  :MANTJAL  OF  ORGANIC  CHEMISTRY 

Only  through  the  intimate  acquaintance  made  in  the  labor- 
atory in  the  actual  handling  and  the  preparation  and  purifica- 
tion of  compounds  can  the  student  hope  to  gain  a  thorough, 
comprehensive  knowledge  of  the  properties  and  reactions  of 
organic  substances.  Study  the  experiments  first  with  the  aid 
of  the  text-book  and  afterwards  carry  them  out  in  the  laboratory. 
Always  read  through  the  entire  experiment  before  beginning  any 
work  in  the  laboratory.  It  is  most  important  THAT  YOU  KNOW 

WHAT  YOU  ARE  DOING  WHEN  YOU  ARE  DOING  IT. 

Wherever  possible  save  time  by  looking  ahead  and  working 
on  more  than  one  experiment  at  a  time. 

Neatness  will  be  insisted  upon  in  all  laboratory  work.  Set 
up  your  apparatus  neatly  and  in  good  shape,  and  do  not  allow 
unnecessary  and  unused  apparatus  to  collect  around  it.  Keep 
the  desk  top  free  from  dirt  and  oil  spots.  The  apparatus  in 
the  cupboards  of  the  desks  should  be  clean  and  neatly  arranged. 
The  desks  will  be  inspected  by  the  instructor  periodically. 

All  apparatus  and  chemicals  must  be  placed  within  the 
desk  at  the  end  of  each  laboratory  period.  Whenever  it  is 
necessary  to  leave  apparatus  on  the  desk  a  "red  tag"  permit 
will  be  issued  by  the  instructor.  In  such  cases  do  not  leave 
out  burners,  or  any  other  disconnected  pieces  of  apparatus. 

Grades. — The  laboratory  grade  will  be  based  upon  (i) 
the  quality  and  yield  of  preparations,  and  (2)  the  general  man- 
ner in  which  the  student  performs  his  laboratory  work,  includ- 
ing his  manipulation,  neatness,  knowledge  of  the  experiment 
while  the  work  is  being  done  as  evidenced  by  replies  to  oral 
questions,  etc.  This  second  part  is  given  several  times  the  weight 
of  the  first. 

Note-books. — It  is  recommended  that  each  student  keep 
a  note-book.  Two  pages  should  ordinarily  be  allowed  for  each 
experiment:  the  left-hand  page  for  the  Type  of  Reaction,  the 
Object  of  the  Experiment  (for  example,  the  Preparation  of 
Ethylene  dibromide  from  Ethylene  and  Bromine),  the  Equa- 
tion for  the  Reaction,  Materials  to  be  used,  any  special  notes, 
and  references;  and  the  right-hand  page  for  the  Method  of 
Preparation,  B.P.  or  M.P.  of  Substance  as  found,  Yield,  Theo- 


GENERAL  NOTES  AND  SUGGESTIONS  3 

retical  Yield  and  Percentage  Yield,  which  is  the  actual  yield 
multiplied  by  100  and  divided  by  the  theoretical  yield,  Chemical 
and  Physical  Properties,  Notes,  and  any  other  data.  The  topics 
for  the  left-hand  page  given  above  refer  particularly  to  the 
"preparations."  For  other  experiments  use  special  topics  as 
needed.  Make  the  Method  of  Preparation  or  Procedure  con- 
cise: do  not  rewrite  the  directions  as  given  in  the  laboratory 
directions.  Use  constitutional  formulas  throughout.  The 
left-hand  page  should  be  written  up  before  the  apparatus  is 
assembled  and  the  experiment  started.  The  right-hand  page 
should  be  written  up  immediately  after  the  experiment  is  com- 
pleted. Be  brief. 

Amounts  of  Chemicals. — In  every  case  carefully  weigh  or 
measure  out  all  chemicals,  regardless  of  what  amount  may  be 
stated  on  the  label.  If  a  horn-pan  balance  is  used  for  weigh- 
ing, place  papers  in  the  scoops.  Sometimes  the  exact  amount 
is  not  necessary,  as  in  the  methane  experiment.  Although  the 
laboratory  work  in  organic  chemistry  is  not  carried  out  with 
the  same  degree  of  accuracy,  as  for  example  in  quantitative 
analysis,  the  best  results  are  obtained  only  when  molecular 
quantities  are  used,  and  these  are  usually  given  in  the  direc- 
tions. Chemicals  should  generally  be  weighed  to  the  first 
decimal  place. 

For  a  liquid,  the  specific  gravity  equals  the  weight  divided 
by  the  volume.  This  simple  expression  should  always  be  borne 
in  mind  when  making  calculations  where  liquids  are  involved. 

Cutting  Sticks  of  Solid  Sodium  or  Potassium  Hydroxide. — 
Caustic  alkali  should  not  be  handled  with  the  fingers.  Put 
the  stick  on  a  piece  of  filter  paper,  and  turn  up  one  side  as  a 
buffer.  A  common  knife  and  a  sharp  blow  upon  it  will  quickly 
cut  off  the  desired  amount.  Protect  the  eyes  with  goggles. 
For  alkali  in  the  eye,  use  castor  oil.  (See  p.  6.) 

Rubber  Stoppers  should  not  be  left  in  any  piece  of  apparatus 
which  has  been  heated.  They  should  be  removed,  if  possible, 
as  soon  as  the  heating  is  discontinued.  Otherwise  the  stopper 
will  be  molded  to  the  shape  of  the  opening  by  the  contraction 
of  the  glass  in  cooling. 


4  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

Loosening   Ground  %lass   Stoppers  and   Stop-cocks. — The 

following  is  very  often  efficient  in  loosening  glass  stoppers  and 
stop-cocks.  Give  a  stout  piece  of  twine  one  or  two  turns  around 
the  neck  of  the  bottle  and  heat  the  glass  by  drawing  the  string 
rapidly  back  and  forth. 

In  case  this  method  does  not  work,  compare  opening  of 
bromine  bottles,  Note  3,  p.  33. 

An  excellent  method  of  removing  "frozen"  stop-cocks  is 
given  by  V.  C.  Allison  (Journ.  Ind.  and  Eng.  Chem.,  11  (1919), 
468).  The  handle  of  the  key  is  slipped  into  a  socket  in  a  block 
of  hard  wood  while  the  opening  of  the  block  rests  as  a  collar 
on  the  shoulder  of  the  barrel  of  the  stop-cock.  A  plug  of  wood 
is  placed  against  the  other  end  of  the  key,  and  easy  regular 
pressure  brought  to  bear  by  means  of  a  vise.  Different  sizes 
are  given  for  the  ordinary  stop-cocks  in  use.  The  scheme  is 
rapid  and  it  works! 

Following  are  the  names  of  three  concise  and  valuable  handy 
books  which  contain  a  large  amount  of  chemical  data  in  com- 
pact ready-reference  form: 

Van  Nostrand's  "Chemical  Annual,"  8vo;  "  Chemiker- 
Kalender"  (German),  2  vols.,  i2mo;  "Handbook  of  Chemistry 
and  Physics,"  yth  Ed.,  1919,  published  by  The  Chemical  Rubber 
Co.,  Cleveland,  O.,  i2mo. 

Collection  of  Liquid  Specimens  in  the  "  Preparations." — 
In  the  Boiling-point  Experiment  (Experiment  No.  i)  you  will 
observe  the  influence  of  radiation,  superheating,  etc.,  and  this 
will  give  you  an  idea  as  to  how  even  pure  liquids  behave  during 
distillation  in  the  ordinary  apparatus.  When  you  are  making 
pure  specimens  the  behavior  of  these  pure  liquids  should  be 
kept  in  mind.  There  will  be  a  small  portion  passing  over  within 
2-3°  before  the  temperature  has  reached  the  proper  boiling- 
point,  and  another  small  portion  near  the  end  as  the  temperature 
rises  2°  or  3°.  Usually  in  ordinary  laboratory  "preparation" 
work  these  first  and  last  runnings  are  collected  along  with  the 
major  portion  distilling  at  a  constant  temperature  and  the 
entire  amount  weighed  as  a  specimen.  Material  boiling  below 
or  above  these  limits  should  be  discarded.  On  the  label  state 


GENERAL  NOTES  AND  SUGGESTIONS  5 

the  range  of  temperature  in  which  the ''material  was  collected 
and  also  give  the  corrected  boiling-point  where  the  temperature 
remained  constant  for  a  long  interval. 

Sodium  Residues. — Great  care  should  be  exercised  in  handling 
residues  of  sodium.  It  should  not  be  put  into  the  sink  or  the 
waste  jar,  but  should  always  be  destroyed  by  adding  it  in  small 
pieces  to  some  alcohol  or  acetone  in  a  beaker,  waiting  until 
practically  all  action  has  ceased  with  each  piece  before  adding 
another.  Then  very  carefully  pour  the  solution  into  the  sink. 
Also  rinse  the  flask  with  alcohol  or  acetone  before  adding  any 
water. 

In  the  laboratory  directions  which  follow,  very  detailed 
directions  are  given  at  first.  Later,  when  the  general  manipula- 
tion should  be  well  understood  all  the  details  are  not  given. 
Then  the  experience  gained  in  the  earlier  part  of  the  course 
should  be  properly  used  when  necessary. 

The  organic  laboratory  is  open  during  definite  hours  on 
the  regular  days  and  it  is  expected  that  students  will  do  all 
their  work  during  these  specified  times. 

Plan  your  work  and  work  your  plan! 

You  can  more  readily  show  your  interest  in  organic  labora- 
tory work  by  carrying  it  out  according  to  well-studied  plans 
than  by  dilly-dallying  along  at  all  hours  and  wasting  your  time 
and  the  time  of  others  also! 

Don't  leave  the  gas,  water,  blast  or  steam  turned  on  for  any 
reason  whatsoever  when  you  leave  the  laboratory. 

Don't  make  any  unnecessary  noise  in  the  laboratory.  (Please 
note  especially  in  the  use  of  the  air  blast.) 

Don't  forget  that  you  will  not  get  any  more  out  of  your  work 
than  you  put  into  it! 


In  Case  of  ACCIDENT  or  FIRE 

FIRE. — Fire  extinguishers  are  hung  up  all  around  the  room. 
In  case  of  burning  oil  use  the  powdered  sodium  bicarbonate 
in  the  bottles  on  the  racks. 

The  blankets  are  for  wrapping  round  a  person  whose  cloth- 
ing is  on  fire.  If  necessary,  use  the  needle  showers. 

ACCIDENT. — On  the  special  shelf  in  the  laboratory  are: 
Boric  acid  solution,  saturated,  for  the  eyes. 
(Eye-cups  hang  below  shelf.) 

Acetic  acid,  1  per  cent  solution,  for  washing  alkali  from 
the  skin. 

Carron  oil  (half  linseed  oil  and  half  lime  water),  for  all 
kinds  of  burns,  including  alkali  and  acid  burns  on  skin. 
Shake  well  before  using. 

Castor  oil  for  eye  burns,  especially  alkali  in  the  eye. 
There  is  a  first  aid  kit  in  the  instructor's  laboratory. 

ACIDS. — On  skin:  wash  with  much  water  immediately,  then 
with  dilute  sodium  bicarbonate.  Use  carron  oil  (on  shelf); 
on  clothing:  wash  with  dilute  ammonium  hydroxide 
solution. 

ALKALIES. — In  the  eye:  use  saturated  boric  acid  on  shelf  if 
injury  is  slight.  Drop  castor  oil  into  the  eye;  on  skin:  wash 
with  much  water,  then  with  dilute  acetic  acid,  i  per  cent 
solution,  or  saturated  boric  acid  solution.  Use  carron  oil; 
on  clothing:  use  some  weak  acid  like  acetic  or  boric,  wash, 
and  then  neutralize  any  remaining  acid  with  ammonium 
hydroxide  or  ammonium  carbonate. 

BROMINE. — On  skin:  wash  with  any  solvent,  like  alcohol, 
benzene,  gasolene,  benzine,  carbon  tetrachloride,  or  dilute 
sodium  bicarbonate.  Then  treat  with  carron  oil  or  car- 
bolated  vaseline. 

NOTE. — Post  a  copy  of  this  sheet  on  the  bulletin  board  and  also 
give  the  name  and  telephone  number  of  the  nearest  physician  and 
the  nearest  hospital. 


Experiment  No.  1 1 

Determination  of  the  Boiling-point  and  Standardization  of  the 
Thermometer  in  the  Ordinary  Distilling  Apparatus 

One  of  the  characteristic  physical  constants  of  a  liquid  is 
its  boiling-point,  and  a  compound  is  generally  considered  pure 
when  it  distills  at  a  constant  boiling-point,  under  constant  pres- 
sure. It  may  also  aid  in  the  identification  of  a  compound. 
In  regular  laboratory  work  it  is  determined  by  means  of  a  ther- 
mometer in  a  distilling  flask  and  the  temperature  of  the  vapor 
entering  the  outlet  tube  is  recorded  as  the  boiling-point  of  the 
liquid.  Obviously  in  this  method,  when  the  ordinary  long-scale 
360°  thermometer  is  used,  there  are  several  errors,  of  which 
the  following  are  most  important:  the  true  boiling-point  is  not 
usually  found  because  the  entire  column  of  mercury  is  not  sur- 
rounded by  the  vapor,  the  vapor  is  easily  superheated,  and 
the  thermometer  may  be  inaccurate.  Since  the  boiling-point 
of  each  liquid  compound  prepared  in  the  course  must  be  deter- 
mined with  a  fair  amount  of  accuracy,  the  thermometer  must 
be  standardized  at  the  beginning,  and  in  order  that  any  cor- 
rection found  may  apply  in  the  regular  work  the  same  general 
form  of  apparatus  will  be  used  in  the  standardization  as  in  the 
regular  work. 

The  error  due  to  the  cooling  of  the  column  of  mercury  which 
extends  above  the  stopper  of  the  flask,  and  therefore  out  of  the 
vapor  of  the  boiling  liquid,  often  amounts  to  6°  or  7°  for  high- 
boiling  liquids.  It  can  be  corrected  as  described  in  the  notes 
at  the  end  of  the  experiment,  but  the  method  of  correction  is 
open  to  grave  errors,  since  it  is  seldom  possible  and  not  always 
convenient  to  obtain  the  required  average  temperature  of  the 

1Have  you  read  over  the  section  entitled  "General  Notes  and  Suggestions"? 
p.  i. 

7 


8  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

exposed  mercury  column.  Furthermore  this  correction  varies 
and  must  be  made  every  time  a  distillation  is  carried  out.  This 
so-called  "stem  correction"  can  be  obviated  by  using  a  ther- 
mometer with  a  short  scale  and  of  such  a  size  that  the  entire 
column  of  mercury  will  be  surrounded  by  the  vapors  of  the 
boiling  liquid.  In  order  that  the  ordinary  range  of  boiling- 
points  of  common  liquids  may  be  covered  you  will  use  a .  set 
of  three  thermometers1  each  one  of  which  has  a  short  scale 
with  a  total  range  of  120°,  No.  i,  15°  to  135°;  No.  2,  95°  to 
215°;  No.  3,  175°  to  295°.  (See  Fig.  i.)  These  thermometers 
"over-lap"  each  other  by  40°,  and  this  makes  it  possible  to  choose 
the  one  which  can  be  employed  to  the  best  advantage.  Pure 
liquids  will  be  used  in  the  tests  and  a  comparison  experiment 
will  be  made  in  at  least  one  instance  to  show  the  extent  of  the 
stem  correction  by  using  both  a  short-scale  and  a  long-scale 
thermometer2  with  the  same  liquid  (aniline). 

The  error  due  to  superheating  can  be  made  a  minimum  by 
proper  heating  of  the  liquid  in  the  flask. 

The  temperature  which  is  obtained  under  conditions  where 
the  errors  mentioned  above  have  been  eliminated  or  reduced 
to  a  fraction  less  than  the  error  of  observation  is  generally 
considered  as  the  corrected  'boiling-point.  Such  a  temperature 
when  written  is  followed  by  the  abbreviation  "cor."  This  dis- 
tinguishes it  from  the  multitude  of  unqualified  (meaning  gener- 
ally uncorrected)  boiling-points  which  unfortunately  fill  the 
literature  and  text-books.  More  corrected  boiling-points  are 
now  being  reported  than  ever  before,  and  this  is  a  good  omen 
for  future  work.  It  is  hoped  that  henceforth  an  unqualified 
boiling-point  will  mean  a  corrected  boiling-point.3  If  the  cor- 

1  The  markings  on  solid  stem  thermometers  often  become  very  dim  and  dif- 
ficult to  read  on  account  of  the  loss  of  the  blackening  from  the  fine  lines.    This 
can  be  remedied  by  rubbing  a  little  graphite  over  the  lines  and  wiping  off  the 
excess. 

2  A  method  of  standardizing  a  long-scale   thermometer  is  described  in  the 
notes,  p.  20. 

3  Even  this  book  contains  some  boiling-points  which  are  unqualified,  since  it 
has  not  always  been  possible  to  find  the  data  in  the  literature  or  to  obtain  the 
pure  materials,  etc.,  necessary. 


o. 


.ex 


7T 


135' 


215° 


+-2951 


I 

4 


-15 


Hi,, 

i.d 


FIG.  i.— Short  Scale  Thermometers. 

Manutactured  by  Eimer  &  Amend,  N.  Y.,  and  sold  under  the  name  of  Fisher  Organic 

Thermometers. 
Q 


10  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

rected  boiling-point  is  for  a  pressure  other  than  760  mm.,  the 
pressure  is  placed  as  a  subscript  before  the  temperature,  for 
example,  "b.p.  735  99°  cor." 

Set  up  a  distilling  apparatus,  using  a  60  cc.  distilling-flask, 
style  B  (Fig.  2),  and  a  condenser1  with  straight  inner  tube. 
Clamp  the  flask  securely,  but  not  too  tightly,  above  the  outlet 
tube  (why?)  and  if  possible  just  under  the  lip.  (Why?) 
Select  the  thermometer  which  has  the  right  temperature  on 
the  scale  where  it  will  be  surrounded  by  the  vapor  of  the  liquid 
(water,  in  the  first  distillation)  and  fasten  it  in  the  neck  of  the 
flask  with  a  sound  well-bored  cork.  Fasten  the  outlet  tube  in 
the  larger  end  of  the  condenser.  The  outlet  tube  should  pass 
far  enough  into  the  condenser  that  the  vapors  will  be  delivered 
directly  into  the  part  of  the  condenser  that  is  surrounded  by 
the  water.  (Why?).  Compare  upper  sketch  in  Fig.  3. 

The  bulb  of  the  thermometer  should  be  placed  just  below 
the  outlet  tube,  but  not  in  the  bulb  of  the  flask,  and  never  in 
the  liquid.  (Why?)  It  must  not  touch  the  walls  of  the  tube. 
(Why?)  Be  sure  that  the  cork  does  not  cover  up  the  thermometer 
where  the  degrees  must  be  seen.  In  this  event  raise  or  lower 
the  thermometer,  or  cut  off  a  complete  portion  of  the  cork  or 
exchange  the  flask.  When  the  short-scale  thermometers  are 
used  this  difficulty  will  seldom  be  encountered. 

Soften  the  selected  cork  by  means  of  a  cork  press.  (There 
are  *cork  presses  on  the  side  walls  of  the  laboratory.)  Or  wrap 
it  in  a  filter  paper  and  roll  it  under  foot.  Make  a  hole  with  a 
sharp  cork-borer  which  has  a  slightly  smaller  diameter  than  the 
desired  opening.  Hold  the  cork  in  the  hand  and  turn  the  borer 
gently  by  means  of  the  rod,  which  should  be  inserted  through  the 
holes  in  one  end  of  the  borer.  In  order  to  bore  the  hole  straight 
it  is  often  found  convenient  to  keep  turning  the  cork  in  the 
left  hand  after  each  slight  twist  of  the  borer,  and  not  take  the 
right  hand  from  the  handle  of  the  borer  at  all.  If  the  cork  is 
placed  on  the  desk,  the  borer  under  excessive  pressure  gouges 
out  the  inside  of  the  cork  and  in  addition  plunges  through  to 

1When  the  word  "condenser"  is  used  it  ordinarily  means  a  condenser  with 
water  jacket  (Liebig  condenser). 


LABORATORY  EXPERIMENTS 


11 


STYLE-A 

Ou-Hef  for  Low 
BoiJing  Liquids 


STYLC-B 

Medium  Ou-Hei-  for  Medium 
Boiling  Liquids 


STYLE -C 

Low  Outlet  for  High 
Boiling  Liquids 


ORDINARY 
DISTILLING  FLASKS 


LADENBURG 

Distilling 
Flask  " 


DISTILLING  FLASKS 


FIG.  2, 


12  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

the  hard  surface  of  the  stone  covering,  and  its  cutting  edge  is 
ruined.  As  a  rule  it  is  well  to  pull  out  the  borer  when  it  is  half 
through  the  cork,  and  push  out  the  cork  plug  inside  before  con- 
tinuing the  boring.  In  this  way  a  clean,  even  cut  is  made 
throughout.  Use  a  rat-tail  file  to  enlarge  the  opening  and  make 
it  fit  tightly.  Place  the  cork  on  the  desk  and  run  the  file  back  and 
forth,  always  pressing  downwards  and  meanwhile  rolling  the 
cork.  The  cork  should  slide  over  the  tube  with  only  moderate 
pressure.  Never  try  to  thrust  a  tube  through  a  cork  of  too  small 
aperture;  an  injured  finger  or  hand  is  very  inconvenient,  if 
not  useless,  for  laboratory  work.  Take  hold  of  the  tube  near 
the  cork  and  twist  it  slowly  as  it  is  carefully  forced  in.  It  is 
advisable  to  use  new  corks  as  much  as  possible  in  organic  work, 
and  therefore  a  good  supply  of  the  different  sizes  should  always 
be  kept  on  hand. 

Always  remove  the  stopper  from  a  flask  or  condenser  before 
changing  the  position  of  any  glass  tube  or  thermometer  in  the 
hole  of  the  stopper. 

Set  the  condenser  at  a  convenient  angle  so  that  the  condensed 
liquid  will  drop  directly  into  the  receiver,  which  should,  as  a 
rule,  rest  upon  the  desk.  Use  a  large  condenser  clamp,1  with 
the  two  prongs  underneath,  and  turn  the  heavy  base  of  the  stand 
toward  you  where  it  will  be  underneath  the  condenser.  The 
base  of  the  stand  to  which  the  distilling-flask  is  attached  should 
also  be  underneath  the  flask  and  turned  toward  you.  It  is  not 
always  necessary  that  the  distilling-flask  be  absolutely  vertical. 
The  positions  of  the  flask  and  the  condenser  can  conveniently 
be  arranged  before  connecting  any  parts  of  the  apparatus  by 
putting  them  in  place  with  the  upper  part  of  the  condenser  in 
line  with,  but  just  behind,  the  outlet  tube  of  the  flask.  Then 
when  the  apparatus  has  been  adjusted  for  the  proper  angles, 
the  condenser  can  be  slid  down  through  the  large  clamp  and 
then  brought  up  around  the  outlet  tube  of  the  distilling-flask 
and  fastened. 

In  case  it  is  desired  to  disconnect  the  distilling-flask  with- 

1  The  prongs  of  all  clamps  should  be  protected  with  white  rubber  tubing 
or  strips  of  cork  or  felt, 


LABORATORY  EXPERIMENTS 


13 


f 

Ordinary  Distillation  Apparatus 

With  Li ebig  straight  water  condenser  and  Erlenmeyer 
f/ask  as  receiver 

\ 


with  Mention -tube 

and  ref/ux  (bulbed)  water 
condenser  attached 


Flask  and^J/r 
Condenser  connected 
with  a  bent  tube 


Calcium    Chloride 
Tube 


FIG.  3. 


14  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

out  changing  the  clamps  and  adjustments,  it  is  easier  to  do  this 
by  loosening  the  stopper  in  the  upper  part  of  the  condenser 
and  allowing  the  condenser  to  slide  down  through  the  large 
clamp  before  removing  the  distilling-flask,  rather  than  to  dis- 
arrange the  setting  of  the  clamps  and  stands  by  taking  away 
the  distilling-flask  first.  After  the  distilling-flask  is  ready,  with 
fittings  made,  etc.,  and  clamped  in  the  original  position,  the 
condenser  can  then  readily  be  replaced  and  connected  without 
changing  the  angle  and  main  position  of  any  clamp. 

The  upper  outlet  for  water  from  the  condenser  should  be 
above  the  jacket  so  as  to  give  the  maximum  condensing  sur- 
face since  the  condenser  will  then  be  full  of  water.  It  should 
be  somewhat  slanted  so  that  the  rubber  tube  which  carries  the 
waste  water  will  not  kink.  The  rubber  tubes  slip  on  easily  if 
a  drop  of  water  is  used  as  a  lubricant  or  if  moistened  by  means 
of  the  breath. 

Use  a  small  Erlenmeyer  flask  as  the  receiver.1 

Add  15  cc.  of  distilled  water  to  the  distilling-flask,  using 
a  funnel  whose  stem  reaches  below  the  opening  of  the  outlet 
tube,  and  drop  in  several  small  pieces,  not  dust  particles,  of 
porous  tile  to  prevent  bumping.  Heat  the  flask  directly2  with 
a  small  blue  flame3  not  over  i  cm.  in  height,  giving  it  a  rotary 
motion  at  first,  and  hold  the  burner  obliquely  so  that  in  case 
the  flask  breaks  the  hand  will  not  be  in  danger.  When  the 
liquid  distills  regularly  the  burner  should  be  set  directly  under- 
neath and  with  the  flame  touching  the  flask.  Do  not  heat  the 
surface  above  the  liquid  as  this  will  superheat  the  vapors.  Avoid 
drafts;  use  a  conical  metal  shield  chimney  for  the  burner  or  a 
large  wind  shield  for  the  apparatus. 

The  temperature  will  rise  rapidly  at  first  until  near  the 

1  Such  a  receiver  should  never  be  fastened  to  the  condenser  by  means  of  a 
stopper.     (Why?) 

2  When  a  larger  flask  is  used,  as  in  some  of  the  later  experiments,  it  is  pro- 
tected with  a  wire  gauze  when  being  heated.    This  method,  however,  generally 
tends  to  superheat  the  vapor  and  therefore  gives  high  results  in  distillations. 

8  Such  a  small  flame  can  easily  be  obtained  by  cutting  down  the  supply  of 
air  at  the  same  time  that  the  gas  supply  is  lowered.  Always  regulate  the  gas  sup- 
ply (of  the  Tirrill  burner)  by  means  of  'the  set  screw  at  the  base. 


LABORATORY  EXPERIMENTS  15 

boiling-point  of  the  substance,  and  then  slowly  until  finally 
it  will  remain  practically  constant.  Distill  over  at  least  one-half 
of  the  liquid.1  The  constant  temperature  within  one-half  of 
one  degree  at  which  most,  if  not  all,  of  it  distills  is  noted  as  the 
observed  boiling-point.  Toward  the  end  of  the  distillation  the 
temperature  may  rise  slightly  on  account  of  superheating. 
Record  the  corrected  barometer2  reading  also. 

NOTE:  The  salient  points  in  connection  with  carrying  out  a 
distillation  are  a  stable  and  well  set-up  apparatus,  with  receiver 
resting  upon  the  desk,  the  thermometer  properly  placed,  corks 
well  bored,  and  a  small-sized  flame  used  in  the  right  way  to  prevent 
superheating. 

Next,  carry  out  another  distillation,  using  the  same  amount 
of  pure  aniline,  184.4°  cor->  under  the  same  general  conditions, 
except  that  the  water  condenser  is  replaced  with  an  "air"  con- 
denser3 and  a  style  C  distilling-flask  (Fig.  2)  is  used  instead  of 
style  B.  A  water  condenser  with  no  water  in  it  should  not  be 
used  in  place  of  the  "air"  condenser  because  of  the  danger  of 
cracking  at  the  joints.  A  flask  with  a  low  outlet  tube  is  used 
for  high-boiling  liquids  in  order  to  avoid  too  much  condensation 
and  on  this  account  excessive  heating  which  causes  a  partial 
decomposition  of  the  substance.  The  distilling-flask  and  con- 
denser must  be  clean  and  dry,  and  fresh  porous  tiling  should  be 
used  as  before. 

In  order  to  dry  a  piece  of  apparatus  rapidly,  rinse  it  with 
alcohol  and  then  with  ether  (keep  all  flames  away).  To  remove 
the  ether  vapors  connect  a  glass  tube  leading  almost  to  the 
bottom  of  the  flask  with  the  suction  or  the  blast.  Since  the  air 
from  the  blast  is  likely  to  be  contaminated  with  iron  dust, 

1  The  effect  of  superheating  upon  the  temperature  of  the  boiling-point  can  be 
seen  if  all  the  liquid  is  distilled  over.    There  is  practically  no  danger  of  cracking 
the  flask  if  it  is  made  of  Pyrex  glass. 

2  For  correcting  the  barometer  reading  see  p.  300. 

3  An  air  condenser  is  a  long,  straight,  thin  glass  tube  of  1.0-1.5  cm.  diameter. 
The  inner  tube  of  a  Liebig  water  condenser  makes  a  very  convenient  air  con- 
denser (see  Fig.  3).    It  is  used  when  the  substance  boils  above  about  150-160°. 
If  a  substance  solidifies   readily  it  would  clog  the   condenser,  and  is  therefore 
collected  directly  from  the  end  of  the  outlet  tube.    Compare  Expt.  No.  51,  phenol. 


16  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

oil,  moisture,  etc.,  it  is  better  to  use  the  suction.  The  wash 
alcohol  and  ether  can  be  used  again,  and  should  be  placed  in 
bottles  properly  labeled  and  kept  for  this  purpose.  Acetone 
may  be  used  instead  of  the  alcohol-ether  combination. 

The  substance  distilled  may  have  absorbed  a  little  moisture 
in  the  handling,  etc.  This  will  be  evidenced  by  a  turbidity  in 
the  first  runnings.1 

Repeat  the  distillation  with  pure  aniline,  but  this  time  use  an 
ordinary  long-scale  360°  thermometer  instead  of  the  short-scale 
thermometer.  Compare  the  temperature  obtained  in  each  case. 

Since  the  boiling-point  varies  with  the  air  pressure  a  correction 
must  be  applied  unless  the  barometer  shows  760  mm.  For 
non-associated  liquids,  the  correction2  for  a  difference  of  every 
10  mm.  in  pressure,  in  the  vicinity  of  760  mm.,  may  be  found 
by  dividing  the  absolute  temperature  of  the  boiling-point  by 
850,  that  is, 

Corrected  observed  b.-p.  =  temp.  of  obs.  b.-p.-f 

/273+temp.  of  obs.  b.-p.     760  —  cor.  barometric  readingX 

\       ~~  ~~         ' 


For  associated  liquids,  such  as  alcohols,  acids,  and  hydroxyl 
compounds  generally,  divide  by  1020,  instead  of  850.  Water 
is  an  associated  liquid,  and  aniline  is  a  non-associated  liquid. 

For  a  more  complete  standardization,  two  temperatures, 
one  near  the  bottom  and  one  somewhat  near  the  top  of  the 
scale  of  each  of  the  three  thermometers,  should  be  checked 
up.  The  following  combinations  of  liquids,  all  of  which  are 
found  in  the  list  given  below,  can  be  used:  For  thermometer 
No.  i,  chloroform  and  water;  for  No.  2,  water  and  aniline; 
and  for  No.  3,  aniline  and  quinoline. 

The  following  is  a  list3  of  liquids  which  when  pure  are  suit- 
able for  testing  the  accuracy  of  thermometers  at  the  corrected 
temperatures  for  760  mm.  given: 

1  Regarding  the  absorption  of  moisture  by  pure  liquids  when  handled  in  ordi- 
nary operations,  compare  Young  and  Fortey,  Trans.  Chem.  Soc.,  83  (1903),  65. 

2  Alex.  Smith  and  Menzies,  Journ.  Amer.  Chem.  Soc.,  32  (1910),  907. 

3  Compare  Young,  "Fractional  Distillation,"  10. 


LABORATORY  EXPERIMENTS  1? 


Carbon  bisulfide1 46 .  o° 

Chloroform 61 .3° 

Benzene 80 . 2° 

Water2 100.0° 

Ethylene  dibromide 131 . 2° 

Chlorbenzene 131 . 95 

Brombenzene3 155 . 5 

Aniline 184 . 4 

Nitrobenzene 210.9 

Naphthalene 218.0 

Quinoline 237 . 5 

a-Bromaphthalene 280.4° 

Benzophenone 305 . 9° 

Mercury 356.8 

NOTES  ON  BOILING-POINT  AND  DISTILLATION 

i.  The  boiling-point  of  a  liquid  is  that  temperature  at  which 
the  saturated  vapor  pressure  of  the  liquid  becomes  equal  to  the  external 
pressure,  and  usually  this  external  pressure  is  the  atmospheric  pres- 
sure. 

"The  true  boiling-point  of  a  liquid  is  identical  with  the  condens- 
ing-point  of  its  vapor  under  the  same  pressure,  provided  that  some 
liquid  is  present  and  that  the  vapor  is  not  mixed  with  an  indifferent 
gas  or  vapor,  and  it  is  generally  more  convenient  to  measure  the 
condensing-point  of  the  vapor  than  the  boiling-point  of  the  liquid. 
To  do  this  an  ordinary  distillation  bulb  is  generally  employed." 
Young:  "Fractional  Distillation,"  p.  26. 

"The  correct  boiling-point  of  a  liquid  at  atmospheric  pressure  is 
best  determined  by  wrapping  cotton-wool,  or,  if  the  liquid  attacks 
that  substance,  asbestos,  round  the  bulb  of  the  thermometer.  By 

1  Carbon  bisulfide  's  very  infiammabl   and  great  care  must  be  exercised  in  hand- 
ling and  distilling  it.    A  bath  of  warm  water  can  be  used  for  heating  it,  but  the 
vapor  should  not  be  superheated. 

2  Water  is  the  only  associated  liquid  in  this  list. 

3  Considerable  difficulty  has  been  encountered  recently  in  obtaining  bromben- 
zene  of  the  desired  purity.    That  on  the  market  is  probably  all  prepared  by  direct 
bromination  of  benzene  which  was  not  properly  purified.     Preparation  on  a 
small  scale  from  pure  aniline  by  Sandmeyer's  reaction  is  recommended. 


18  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

this  plan,  even  though  the  vapor  may  be  superheated,  yet  the  liquid 
in  contact  with  the  thermometer  bulb  must  be  at  the  true  boiling- 
point,  since  it  has  a  free  surface  of  evaporation."  Ramsay  and 
Young,  Trans.  Chem.  Soc.,  47,  (1885),  42.  Compare  Cottrell, 
"On  the  Determination  of  Boiling-points  of  Solutions,"  Journ. 
Amer.  Chem.  Soc.,  41  (1919),  721-9;  and  Washburn  and  Read,  "The 
Laws  of  'Concentrated '  Solutions,  VI,  The  General  Boiling-point 
Law,"  ibid.,  41  (1919),  729-41.  Figures  of  a  special  apparatus  are 
given  in  both  articles. 

For  the  determination  of  correct  boiling-points  a  special  form  of 
apparatus  is  used  in  which  ah1  possible  errors  from  superheating, 
radiation,  etc.,  are  provided  against.  Short-scale  thermometers 
which  are  made  of  normal  glass  and  which  have  been  properly  stand- 
ardized are  employed.  Normal  glass  is  a  special  glass  that  has  been 
aged  by  suitable  treatment  of  heating,  etc.,  until  its  behavior  on 
further  heating  and  cooling  has  become  uniform.  Such  thermometers 
can  be  obtained  with  certificates  showing  the  results  of  standardization 
by  certain  bureaus  of  different  governments,  like  the  U.  S.  Bureau 
of  Standards. 

2.  A  liquid  ought  to  boil  as  soon  as  its  vapor  pressure  becomes 
slightly  greater  than  atmospheric,  but  it  is  a  well-known  fact  that 
boiling  does  not  necessarily  take  place  under  these  conditions.  Most 
liquids  can  readily  be  superheated.1  The  transformation  of  a  liquid 
into  the  vapor  phase  will,  however,  take  place  immediately  if  the 
vapor  phase — any  inert  gas — be  introduced,  but  not  otherwise.2 
For  comparison  we  have  the  supercooling  of  a  liquid  which  will  solidify 
as  soon  as  a  particle  of  the  solid  phase  is  added,  for  example,  ice 
in  supercooled  water. 

Superheating  cannot  take  place  at  the  surface  of  a  liquid  since 
there  the  liquid  is  always  in  contact  with  the  vapor  phase.  It  always 
takes  place  in  the  interior  and  especially  at  the  bottom  where  the 
heat  is  applied.  It  is  of  course  not  possible  to  go  an  unlimited  dis- 
tance into  the  metastable  "area,"  since  the  further  away  we  get 

1  It  is  of  interest  to  note  that  chloroform,  which  ordinarily  boils  at  61°,  has  been 
heated  to  a  temperature  of  100°  by  suspending  the  drops  in  a  zinc  chloride  solu- 
tion of  the  same  specific  gravity,  and  that  water  has  similarly  been  heated  to  170° 
by  suspending  it  in  a  mixture  of  oils.     (Dufour,  Arch,  de  la  Bibl.  univ.  (1861) 
T.  XII,  210;  and  Poggendorfs  Annalen,  124  (1865),  295.) 

2  Aitken,  "On  boiling,  condensing,  freezing,  and  melting,"  Trans.  Royal  Scot- 
tish Society  of  Arts,  9  (1875),  240-87;    Duhem,  "Thermodynamics  and  Chem- 
istry," trans,  by  Burgess,  (1913),  365-8- 


LABORATORY  EXPERIMENTS  19 

from  equilibrium  the  greater  is  the  tendency  for  the  system  to  come 
to  equilibrium.  Finally  this  tendency  will  become  so  great  that  the 
system  will  be  able  to  overcome  its  reluctance  to  a  change  of  phase, 
vaporization  will  then  take  place  suddenly  and  sometimes  with  great 
violence — in  other  words,  bumping  occurs.  Stirring 1  helps  to  prevent 
bumping,  since  the  liquid  is  thus  evenly  heated  and  vaporization 
will  take  place  readily  at  the  surface,  as  mentioned  above.  The 
best  means  to  prevent  bumping  is  to  introduce  the  vapor  phase 
directly,  and  this  is  done  in  several  ways,  (i)  By  passing  a  stream  of 
air  bubbles  through  a  capillary  tube  into  the  liquid  (see  Expt.  No.  15, 
Vacuum  Distillation).  (2)  Another  method  which  is  very  convenient 
for  a  short  period  is  to  place  in  the  liquid  a  small  glass  tube,  about 
i  mm.  in  diameter  and  sealed  at  one  end.  It  should  be  long  enough 
to  stand  upright,  and  when  in  position  the  open  end  should  be  at  the 
bottom.  On  warming  the  liquid  the  air  in  the  tube  expands  and 
bubbles  through  the  liquid.  If  the  distillation  is  interrupted,  a 
new  tube  must  be  introduced.  (3)  By  using  pieces  of  porous  tiling 
which  contains  a  large  amount  of  air.  Pumice  cannot  be  used  so 
well,  since  it  floats  in  most  liquids  and  therefore  does  not  introduce 
the  air  bubbles  at  the  seat  of  the  trouble.  Glass  beads,  and  many 
substances  with  "points"  are  often  used  to  prevent  bumping,  but 
their  efficiency  does  not  depend  upon  their  "points,"  but  upon  the 
air  which  is  adsorbed  on  their  surfaces.  As  soon  as  this  air  has  been 
driven  off  they  are  no  longer  of  any  use,  unless  they  are  removed, 
dried  and  heated  before  being  used  again.2  Even  platinum  "tri- 
angles" after  a  time  must  be  removed,  heated,  and  allowed  to  cool 
in  the  air  before  being  introduced  again.3  Fine  particles  of  any  sub- 

1  Morgan,  "The  Elements  of  Physical  Chemistry,"  sth  Ed.,  (1914),  i?8.       ' 

2  Ostwald-Luther,   " Physiko-chemische  Messungen,"  3.  Auflage,   (1910)  219; 
Lehmann,  "Molekiilarphysik,"  (1889),  II,  151. 

3E.  C.  Kendall,  in  a  recent  note,  Journ.  Amer.  Chem.  Soc.,  41  (1919),  1189, 
states  that  carbon  in  certain  forms  is  an  excellent  aid  to  produce  rapid  boiling* 
"It  was  found,  however,  that  the  various  forms  of  carbon  differ  greatly  in  their 
power  to  cause  rapid  boiling  of  a  solution.  While  powdered  charcoal  or^coke  has 
slight  power  in  this  respec  ,  anthracite  coal  is  without  exception  j$ie  very  best 
substance  to  bring  about  the  rapid  boiling  of  a  solution.  The  formation  -6f  bub- 
bles does  not  take  place  on  the  sharp  edges  and  corners  .alone,  but  over  the  hard, 
smooth  surfaces  of  the  coal  minute  bubbles  form  witrr^freat  rapidity,  and  under 
some  conditions  a  piece  of  coal  2  cm,. .cube  can  be  raised-from  the  bottom  of  the 
flask  by  the  rapid  formation  of  bubbles  on  its  surface.  It  acts  in  a  similar  man- 
ner in  the  acidification  of  a  carbonate  «r  sulfite  solution If  the  coal  is 

kept  under  water  indefinitely  it  becomes  less  active,  but  heating  in  an  oven  will 


20  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

stance   rapidly  lose  their   adsorbed  air  and  then  they  increase  the 
tendency  to  bumping  instead  of  decreasing  it.1 

3.  The  "stem  correction,"  in  degrees  =  -\-N(t— t')o.oooi$4, 
where  N  =  that  portion  of  the   mercury  column  which  is  not  heated 

by  the  vapors,  read  in  degrees; 
/= observed  boiling  temperature; 

/'= average  temperature  of  the  exposed  column  of  mercury 
as  found  by  a  second  thermometer  hung  beside  the  first 
one; 
0.000154  =  coefficient  of  apparent  expansion  of  mercury  in  glass. 

4.  Standardization  of  a  long-scale  thermometer. 

A  long-scale  thermometer  is  standardized  by  locating  certain 
points  found  by  means  of  the  boiling-points  of  pure  liquids  such  as 
those  on  p.  17,  and  also  the  freezing-point  of  water,  and  then  by 
plotting  these  results  on  co-ordinate  paper  the  correction  for  any 
one  degree  may  be  read  off  at  any  time.  The  correction  is  of  course 
larger  as  the  boiling-point  •  increases,  and  often  amounts  to  several 
degrees  for  higher-boiling  liquids.  The  results  are  applicable  only 
for  the  particular  distilling  flasks  used  in  obtaining  the  data. 

On  a  piece  of  cross-section  millimeter  paper,  100X300  mm., 
mark  on  the  lowest  heavy  horizontal  line  as  the  abscissa  the  degrees 
of  the  thermometer  every  50°,  counting  each  millimeter  as  a  degree. 
The  corrections  are  generally  to  be  added,  and  are  therefore  plotted 
above  the  main  line.  If  any  minus  corrections  are  found,  the  heavy 
horizontal  line  chosen  must,  of  course,  be  far  enough  above  the  bot- 
tom of  the  sheet  to  allow  space  for  the  proper  corrections.  The 
amount  of  the  correction,  that  is,  the  difference  between  the  "cor- 
rected observed  reading"  and  the  true  boiling-point  at  760  mm., 
is  plotted  on  a  perpendicular  line  as  an  ordinate,  opposite  the  num- 
ber on  the  abscissa  corresponding  to  the  "corrected  observed  read- 
ing," and  counting  each  centimeter  as  a  degree.  Connect  the  four 
points  thus  found  with  a  smooth  curved  line.  From  this  curve  it 
is  now  possible  to  tell  at  a  glance  the  correction  for  any  degree  as 
follows:  add  to  the  corrected  observed  reading  the  difference  in 
degrees  between  the  main  abscissa  at  the  point  of  the  corrected 
observed  reading  and  the  point  where  its  ordinate  cuts  the  curve. 

restore  its  activity.  .  .  .  One  or  two  pieces  of  about  i  cm.  cube  are  better  than 
many  smaller  pieces." 

1 1  am  indebted  to  a  "seminar"  paper  oh  "Bumping"  by  Mr.  Harold  L.  Simons 
for  most  of  the  material  presented  in  Note  2. 


LABORATORY  EXPERIMENTS  21 

Put  all  the  data  used  in  the  plotting  in  a  convenient  corner  of  the 
same  paper  for  reference. 

The  curve  between  155°  and  180°  is  not  very  accurate  if  the 
style  of  flask  was  changed.  Explain.  Mark  the  standardized  ther- 
mometer for  future  identification  with  a  piece  of  cord  or  wire  in  the 
loop. 

QUESTIONS 

1.  Define  the  boiling-point. 

2.  Give  some  of  the  errors  in  the  ordinary  method  for  deter- 

mining the  boiling-point. 

3.  What   is   a   standardized    thermometer?     a   normal    ther- 

mometer? 

4.  How  is  the  true  boiling-point  determined? 

5.  How  may  this  be  done  for  ordinary  laboratory  conditions? 

6.  What  is  meant  by  the  "stem  correction"?     How  is  the 

"stem  correction"  determined  practically?  How  can  it 
be  obviated? 

7.  Why  should  a  cork  be  softened  before  using? 

8.  When  are  the  different  styles  (A,  B  and  C)  of  distilling-flasks 

used? 

9.  Why  not  place  the  bulb  of  the  thermometer  in  the  liquid? 

10.  Why  is  the  flame  given  a  rotary  motion  at  first? 

11.  Explain  how  the  porous  tiling  aids  the  boiling. 

12.  Why  should  porous  tiling  not  be  added  to  a  hot  liquid? 

13.  What  is  meant  by  an  "associated"  liquid?     A  unon-asso- 

ciated"  liquid? 

14.  Why  is  water  used  in  the  condenser?     Could  mercury  be 

used? 

15.  When  the  same  quantities  of  water  and  aniline  are  each  ) 

separately  distilled  from  the  same  flask  under  identical/ 
conditions  using  the  same  size  flame,  etc.,  why  does  the/ 
aniline  distill  faster  than  the  water  even  though  it  has  a\ 
higher  boiling-point?    (This  behavior  is  particularly  notice- J 
able  in  the  case  of  brombenzene.) 

1 6.  After  the  plot  for  the  corrections  has  been  made  could 

it  be  used  for  finding  the  correction  if  a  distilling-flask 
of  different  style  and  size  were  used  instead  of  one  of 
the  style  and  size  used  when  the  plot  was  made? 


Experiment  No.  2 

FRACTIONAL  DISTILLATION 

Fractionation  of  a  Mixture  of  Ethyl  Alcohol  and  Water 

Measure  separately  in  a  graduated  cylinder  50  cc.  of  ethyl1 
alcohol  (95  per  cent)  and  50  cc.  of  distilled  water  and  mix  the 
two  liquids  in  a  beaker.  Note  the  temperature  of  the  mixture, 
cool  to  the  temperature  of  the  room  by  setting  the  beaker  in 
water  and  then  measure  its  volume  again.  Is  it  exactly  100 
cc.?  Place  i  cc.  of  the  cooled  liquid  into  an  evaporating  dish 
and  apply  a  flame  momentarily.  Do  not  heat  it.  Does  it  catch 
fire?  Transfer  the  dilute  alcohol  to  a  clean  dry  i25-cc.  Laden- 
burg  distilling  flask,2  add  several  small  pieces  of  porous  tile, 
insert  a  thermometer,  and  connect  the  outlet-tube  with  a  con- 
denser having  a  straight  inner  tube.  Make  two  fractionations. 
First  Fractionation. — This  will  consist  of  four  fractions. 
For  receivers  use  clean  dry  Erlenmeyer  flasks,  two  125-0:. 
and  two  6o-cc.,  and  label  them  from  i  to  4,  using  the  larger 
ones  for  the  first  and  last  fractions.  Have  corks  ready  to  fit. 
The  temperature  intervals  at  which  the  fractions  are  collected, 
as  usually  taken,  are  approximately  equal.  The  number  of 
fractions  depends  on  the  substances  and  the  degree  of  separa- 
tion desired.  In  this  experiment  allow  all  that  comes  over  up 
to  83°  to  flow  into  the  receiver  labeled  No.  i.  When  the  tem- 
perature begins  to  exceed  83°  exchange  the  receiver  for  No.  2, 
and  collect  the  fraction  up  to  89°,  similarly  for  No.  3,  89+° 
to  96°,  and  No.  4,  96+°  to  100+°. 

1  Ordinary  alcohol  is  ethyl  alcohol. 

2  A  sketch  of  the  Ladenburg  distilling  flask  is  given  in  Fig.  2.     It  consists 
of  a  distilling  flask  and  a  simple  still  head  (or  fractionating  column)  combined. 
For  supporting  such  a  round-bottomed  flask  when  unattached,  use  a  suberite 
(pressed  cork)  ring. 

22 


LABORATORY  EXPERIMENTS  23 

Heat  the  flask  first  with  a  rotary  motion  of  the  burner. 
Use  a  small  non-luminous  flame  not  more  than  2  cm.  long. 
When  the  liquid  is  distilling  regularly,  set  the  burner  directly 
under  the  center  of  the  flask  with  the  flame  touching  and  do 
not  remove  it  during  the  entire  distillation.  The  drops  of  the 
distillate  should  form  regularly  and  at  such  a  rate  that  they  can 
easily  be  counted,  90-100  a  minute.  Keep  up  this  rate  by  very 
gradually  increasing  the  flame.  The  distillation  takes  about 
thirty  minutes.  The  slower  the  distillation  the  better  is  the  sep- 
aration. On  account  of  superheating,  the  temperature  may  go 
slightly  above  100°  toward  the  end.  It  is  not  necessary  to 
distill  over  all  the  remaining  portion.  Add  it  to  receiver  No.  4, 
cool  under  running  water,  and  then  measure  the  amount  at  the 
ordinary  temperature. 

Measure  the  volume  of  each  fraction,  and  tabulate  the  results 
according  to  the  following  scheme: 

Fraction I  II  HI  IV 

Temperature Up  to  83°      83+°  to  89°      89+°  to  96°      96+°  to  ioo+° 

Volume 20  cc.  31  cc.  8  cc.  40  cc. 

Second  Fractionation. — To  make  a  further  separation  distill 
the  fractions  one  after  another  according  to  the  following  pro- 
cedure: Clean  out  the  distilling-flask  and  pour  into  it  the  first 
fraction.  After  adding  some  new  porous  tile  distill  as  above, 
collecting  the  distillate  up  to  83°  in  receiver  No.  i.  As  the  tem- 
perature begins  to  rise  above  83°,  although  there  will  still  be 
some  liquid  in  the  flask,  interrupt  the  distillation  by  removing 
the  burner.  When  the  flask  is  cool  add  to  it  fraction  No.  2, 
and  again  distill  until  the  temperature  just  exceeds  83°,  col- 
lecting this  distillate  in  the  same  receiver,  No.  i.  Now  add 
similarly  No.  3,  and  finally  No.  4,  collecting  in  each  case  all  that 
distills  up  to  83°  in  receiver  No.  i.  After  No.  4  has  been  added 
do  not  stop  the  distillation  at  83°  but  continue  as  in  the  first 
fractionation,  and  collect  the  distillates  in  receivers  2,  3  and  4, 
at  the  same  temperature  intervals  as  before. 

The  new  results  will  appear  somewhat  as  follows: 

Fraction I  II  III  IV 

Temperature.. Up  to  83°      83+°  to  89°      89+°  to  96°      96+°  to  100° 

Volume 47  cc.  0.5  cc,  7.5  cc.  43.5  cc, 


24  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

Apply  a  flame  to  fraction  No.  i.    Does  it  kindle  now? 

A  third  fractionation  made  as  described  under  the  second 
fractionation  would  lead  to  a  more  thorough  separation  because 
of  the  altered  composition  of  the  fractions.  Furthermore,  any 
single  fraction  may  be  subjected  to  a  similar  process  of  fraction- 
ation by  means  of  which  its  separation  into  alcohol  and  water 
could  be  made  more  nearly  complete. 

A  mixture  of  ethyl  alcohol  and  water  containing  95.57 
per  cent  of  alcohol  by  weight  has  a  minimum  boiling-point, 
78.15°  (760  mm.),  so  that  it  is  not  possible  by  distillation  alone 
to  make  a  separation  beyond  this  point.  Pure  alcohol  boils 
at  78.30°.  Alcohol  of  90.7  per  cent  has  the  same  boiling-point 
as  pure  alcohol. 

NOTE 

The  results  given  in  the  tables  were  obtained  under  the  condi- 
tions described  above,  that  is,  the  distillate  came  over  at  the  rate 
of  about  90-100  drops  a  minute.  Under  similar  conditions,  but 
using  an  ordinary  distilling  flask  instead  of  the  Ladenburg  distilling 
flask,  the  results  are  somewhat  as  follows:  First  fractionation, 
12,  31,  8,  40  cc.,  and  second  fractionation:  40,  2,  10  and  41  cc., 
respectively. 

References  for  collateral  reading  on  the  fractionation  of  liquids 
which  mix  in  all  proportions:  Morgan,  "The  Elements  of  Physical 
Chemistry,"  5th  Ed.  (1918),  177;  Walker,  "Introduction  to  Physical 
Chemistry,"  7th  Ed.  (1913),  84-6;  Washburn,  "Principles  of  Physical 
Chemistry,"  (1915),  180-1. 

Alex.  Smith,  "Introduction  to  Inorganic  Chemistry,"  New  Ed. 
(1917),  fractionation,  587-8;  alcohol  and  water,  609;  other  constant 
boiling  mixtures,  211-2,  273,  279. 

For  the  boiling-point  curve  of  mixtures  of  ethyl  alcohol  and  water, 
see  W.  A.  Noyes  and  Warfel,  Journ.  Amer.  Chem.  Soc.,  23  (1901) 
468. 

A  still-head  described  by  S.  F.  Dufton  in  an  article  on  "The 
limits  of  separation  by  fractional  distillation,"  Journ,  Soc.  Chem.  Ind.y 
38  (1919),  4s;,  is  said  to  be  unusuallv  efficient 


LABORATORY  EXPERIMENTS 


25 


QUESTIONS 

1.  Outline  the  theory  of  fractional  distillation. 

2.  Discuss  the  fractional  distillation  of  the  three  different  cases 

of  liquids  which  mix  in  all  proportions. 

3.  Explain  why  pure  alcohol  is  not  obtained  (See  No.  2). 

4.  Of  about  what  percentage  alcohol  does  the  first  fraction  of 

the  second  fractionation  consist? 

5.  Why  is  the  burner  not  removed  after  the  distillation  has 

begun? 

6.  Would  the  first  fraction  be  increased  or  diminished  if  the 

flask  was  protected  with  a  wire  gauze  during  the  heating? 

7.  What   is   a    "still-head"    or   fractionation   apparatus?     See 

Fig.  4.     Why  used? 


FRACTIONATION  APPARATUS 

WITH 
YOUNG'S  PEAR  STILL-HEAD 


FIG.  4. 


Experiment  No.  3 
Absolute  Alcohol 

The  presence  of  water  in  alcohol  may  be  shown  by  shaking 
3  cc.  with  a  very  little  white  anhydrous  copper  sulfate  in  a  dry 
well-stoppered  No.  i  test-tube.  After  half  an  hour  note  any 
change  in  the  copper  sulfate.  Explain. 

In  the  following  experiment,  ordinary  95  per  cent  ethyl 
alcohol  is  dehydrated  over  quicklime  (CaO).  It  is  then  dis- 
tilled from  the  semi-solid  residue  and  collected  under  anhydrous 
conditions. 

To  a  looo-cc.  flask  attach  the  narrow  end  of  a  slanting 
condenser  with  bulbed  inner  tube  ("reflux"  condenser).  (Com- 
pare Fig.  3.)  The  end  of  the  tube  should  pass  entirely  through 
the  cork  so  that  the  condensed  liquid  will  drop  free  without 
touching  the  cork.  This  is  a  general  rule  always  to  be  followed 
under  similar  condit'ons.  If  there  is  a  small  hole  near  the  end 
of  your  condenser  see  that  it  is  below  the  stopper.  (What  is 
the  object  of  this  small  hole?)  Arrange  the  apparatus  so  that 
the  flask  can  be  heated  on  the  steam-bath.1  Pour  300  cc.  of 
ordinary  alcohol  into  the  flask,  slant  it  and  add  about  150 
grams  of  good  quicklime,  weD  crushed.  (It  should  not  be 
powdered.)  Connect,  and  heat  for  an  hour.  During  this  time  the 
alcohol  will  boil  gently.  If  it  condenses  rapidly  and  the  liquid 
rises  in  the  condenser,  lower  the  temperature  of  the  bath  slightly, 
and  if  necessary  pour  water  over  the  flask.  During  the  heating  it 
is  well  to  attach  the  filled  calcium  chloride  tube  mentioned 
below.  (Why?) 

1  If  a  steam-bath  is  not  handy  or  in  working  order,  use  a  constant-level  water- 
bath  (Fig.  5).  When  working  with  inflammable  liquids  the  flame  under  the  water- 
bath  should  be  enclosed  in  a  chamber  surrounded  by  a  wire  screen,  in  other 
words,  a  "safety  water-bath"  should  be  used. 

26 


LABORATORY  EXPERIMENTS 


27 


If  the  alcohol  is  allowed  to  remain  in  contact  with  the  lime 
for  two  or  three  days,  heating  for  one-half  hour  will  be  sufficient 
before  the  absolute  alcohol  is  distilled. 

Prepare  a  calcium  chloride  tube 1  by  first  inserting  a  loose 
plug  of  glass  wool  or  cotton  into  the  bulb  (not  the  narrow  tube) 
and  then  almost  filling  the  tube  with  small  lumps  of  granular 
calcium  chloride,  free  from  dust  particles,  and  covering  this 


Water 


RubberTube  Connection- 


Overflow  to  drain 


CONSTANT  LEVEL  WATER  BATH 

CROSS     SECTION 
FIG.  5. 

with  another  plug  of  glass  wool  or  cotton.  To  keep  the  contents 
in  place,  and  also  to  prevent  an  undue  circulation  of  air,  insert 
a  cork  containing  a  short  piece  of  glass  tubing  open  at  both  ends. 
If  the  apparatus  is  allowed  to  stand  overnight,  place  the  cal- 
cium chloride  tube  in  the  top  of  the  condenser,  fastening  the 
narrow  end  in  a  cork. 

Also  make  ready  a  condenser  with  straight  inner  tube,  dry 
inside,  and  a  bent  glass  tube  for  connecting  the  flask  with  the 
larger  end  of  the  condenser  in  the  position  for  distillation. 
The  bend  of  the  tube  should  be  just  above  the  cork  stopper,  and 
the  tube  should  be  cut  off  just  below  the  stopper.  (Why?)  For 
the  receiver  attach  a  clean  dry  Erlenmeyer  filter-flask  by  means 

1  See  Fig.  3. 


28  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

of  a  cork  to  the  lower  end  of  the  condenser  and  connect  its  side 
tube  with  the  narrow  end  of  the  calcium  chloride  tube  by  means 
of  rubber  tubing.  Do  not  close  this  tube  with  a  stopper  during 
the  distillation.  (Why?)  The  receiver  should  rest  upon  the 
desk  when  the  apparatus  is  ready  for  use. 

Bending  Glass  Tubing. — Hold  the  dry  tube  lengthwise  in 
the  spreading  even  flame  of  a  /  wing- top  burner.  If  the  wing- 
top  does  not  give  an  even  flame  it  should  be  exchanged  or 
repaired.  Keep  turning  the  tube  until  it  is  soft,  then  remove 
it  from  the  flame  and  bend  to  the  desired  angle.  The  bend  should 
be  round  and  strong,  never  angular.  If  the  tube  is  thick  or  large 
it  must  be  heated  in  the  smoky  flame.  Always  "round"  the 
rough  edges  of  all  glass  tubes  by  holding  them  in  the  flame 
until  the  edges  have  melted.  This  also  applies  to  stirring-rods. 

At  the  end  of  the  hour  cool  the  contents  of  the  flask  by  allow- 
ing a  stream  of  cold  water  to  play  upon  the  flask,  which  should 
be  raised  slightly  in  order  that  the  waste  water  will  run  into 
the  bath.  When  the  alcohol  ceases  to  boil,  connect  the  flask 
as  outlined  above  for  distillation,  and  distill  until  no  more  drops 
come  over,  heating  the  flask  on  the  steam-bath.  Collect  the 
first  10  cc.  in  an  open,  unattached  test-tube,  and  the  remainder 
in  the  filter-flask.  Test  the  lo-cc.  portion  and  a  portion  of  the 
main  distillate  for  moisture.  (?)  The  distillation  may  be 
hastened  by  covering  the  flask  and  bent  tube  with  a  towel  to 
prevent  radiation.  Sometimes  the  liquid  bumps  furiously, 
since  all  the  air  has  been  driven  out  of  the  lime.  (Compare 
the  Boiling-point  Experiment,  Note  2.)  In  this  case,  cool 
thoroughly,  add  a  few  pieces  of  porous  tile,  then  heat  again. 

Keep  the  absolute  alcohol  in  a  dry,  labeled  bottle.  It  will 
be  needed  for  later  experiments. 

Do  not  empty  the  waste  lime  into  the  sink! 


QUESTIONS 

1.  What  is  formed  in  the  test  for  water  in  alcohol? 

2.  Why  is  a  bulbed  condenser  preferable  to  a  straight  condenser 

for  reflux  work? 


LABORATORY  EXPERIMENTS  29 

3.  Why  is  the  bulbed  condenser  not  used  for  the  distillation? 

Could  it  be  used  at  all? 

4.  Why  should  the  quicklime  not  be  powdered?     (Compare 

Note  2,  p.  18.) 

5.  Why  is  a  calcium  chloride  tube  necessary? 

6.  Why  must  the  calcium  chloride  tube  not  be  stoppered  with 

a  cork? 

7.  Why  is  the  first  10  cc.  of  the  distillate  discarded? 

8.  Does  every  part  of  the  distillate  as  it  drips  from  the  con- 

denser contain  the  same  percentage  of  alcohol?  Explain 
fully.  (Compare  with  the  curves  showing  the  boiling- 
point  and  composition  of  the  different  mixtures  of  alcohol 
and  water:  see  Walker's  "  Introduction  to  Physical 
Chemistry/'  ;th  Ed.  (1913),  85.) 

9.  Is  the  "absolute  alcohol"  prepared  in  this  way  absolutely 

free  from  water? 

10.  How  can  the  driest  ethyl  alcohol  be  prepared? 

11.  Why  cannot  the  following  drying  agents  be  used:   calcium 

chloride;  cone,  sulfuric  acid;  phosphoric  anhydride; 
solid  potassium  hydroxide? 


Experiment  No.  4 
Tests  for  Carbon  and  Hydrogen  in  Organic  Compounds 

1.  Effect  of  heat  alone  on  an  organic  substance:    a.  Place  a 
little  cane  sugar  in  a  porcelain  evaporating  dish  and  heat  gently 
with  a  small  blue  flame. 

b.  Repeat  the  above  experiment,  using  benzoic  acid  instead 
of  cane  sugar.  By  using  a  small  flame  all  the  substance  will 
sublime  without  charring,  or  leaving  a  residue.  (The  fumes 
produce  coughing  when  breathed.) 

2.  Carbon  and  Hydrogen  can  be  detected  in  organic  com- 
pounds by  oxidation: 

In  a  porcelain  evaporating  dish  dry  about  2  grams  of  cupric 
oxide  powder  by  heating  to  dull  redness  for  several  minutes. 
While  it  is  cooling,  heat  a  piece  of  glass  tubing  (6  mm.)  about 
15  cm.  long  in  the  Bunsen  flame  at  a  point  10  cm.  from  the  end, 
and  as  it  softens  slowly  draw  it  out  and  seal  it.  Intimately 
mix  a  very  small  amount  of  benzoic  acid  (from  the  end  of  a 
knife  blade)  with  half  the  warm  cupric  oxide,  transfer  this  to 
the  10  cm.  sealed  tube  and  add  the  remaining  cupric  oxide. 
Tap  the  tube  horizontally  on  the  desk  so  as  to  make  a 
channel  above  the  mixture  and  clamp  it  near  the  open  end 
in  a  horizontal  position.  Connect  it  with  a  short  piece  of 
rubber  tubing  to  another  length  of  glass  tubing  bent  at  right 
angles  and  leading  just  below  the  surface  of  3  cc.  of  clear  lime 
water  contained  in  a  No.  i  test-tube.  Now  gently  heat  the 
layer  of  pure  cupric  oxide  and  then  the  mixture.  What  evidence 
is  there  of  the  formation  of  water  and  of  carbon  dioxide? 

QUESTIONS 

1.  What  is  sublimation? 

2.  Why  is  the  glass  tube  not  sealed  by  simply  melting  the  edges 

together? 

3.  What  causes  the  reddish-brown  color  in  the  tube  after  the 

heating? 

4.  How  are  carbon  and  hydrogen  determined  quantitatively? 

30 


Experiment  No.  6 

FORMATION  OF  A  PARAFFIN  HYDROCARBON  BY  REDUCTION  OF 
A  HALOGEN  DERIVATIVE 

Methane   from   Chloroform   and    Chemical   Properties   of   the 
Paraffin  Hydrocarbons 

Fasten  a  125  cc.  Erlenmeyer  flask  upright  with  a  clamp, 
and  place  into  it  10  grams  of  zinc  dust1  and  15  cc.  of  alcohol 
and  10  cc.  of  water.  Insert  a  bent  glass  tube  through  a  well- 
bored  tight-fitting  cork  and  connect  with  a  short  tube  leading 
to  a  beaker  or  small  pail  of  water  arranged  so  that  the  gas  that 
is  formed  may  be  collected  by  displacement.  Now  add  to  the 
flask  5  cc.  of  chloroform  and  2  cc.  of  a  -gV  molar  solution  of  cop- 
per sulfate.  The  reaction  will  soon  begin  spontaneously.  It 
may  even  be  necessary  to  moderate  it  by  cooling  the  flask  with 
some  water.  Collect  two  test-tubes  of  the  gas,  discarding  the 
first  one,  and  then  in  addition  fill  two2  glass-stoppered  bottles 
of  the  capacity  of  the  test-tubes. 

a.  Ignite  the  gas  in  the  test-tube.     (Wrap  the  test- tube 
in  a  towel  before  doing  so,  because  if  the  methane  contains 
air  an  explosion  might  result  of  sufficient  violence  to  shatter 
the  tube.)     Immediately  after  the  gas  is  burned  add  2  cc.  of 
lime  water,  stopper  and  shake.     What  causes  the  turbidity  of 
the  solution?    Why  does  the  gas  made  by  this  method  burn 
with  a  green  flame?    Is  this  characteristic  of  pure  methane? 

b.  To  a  bottle  of  the  gas  add  2  cc.  of  bromine  water  and 
shake.    Is  there  any  change  in  color?    Explain. 

c.  To  5  cc.  of  benzine  ("  benzolene,"  not  benzene,  see  Note  i) 
add  i  cc.  of  a  solution  of  5  grams  of  bromine  in  100  grams  of 

1  See  Note  regarding  weighing  out  chemicals,  p.  3. 

2  One  extra,  in  case  a  second  trial  of  one  of  the  tests  is  required. 

31 


32  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

carbon  tetrachloride.  Divide  into  two  portions,  set  one  in  the 
dark  and  the  other  in  direct  sunlight.  After  several  minutes 
compare  them.  What  has  happened  in  the  one  exposed  to  sun- 
light? Breathe  across  the  top  of  the  tubes.  What  does  the 
formation  of  a  cloud  of  vapor  indicate? 
d.  Stability  of  paraffins  toward  reagents: 

1.  Add  several  drops  of  benzine  to  i  cc.  of  cone,  sulfuric 
acid.    Shake.    Is  there  any  evidence  of  chemical  action  apparent 
by  the  formation  of  heat  or  by  darkening?    Does  the  mixture 
become  homogeneous?     Pour  it  slowly  into  cold  water,  cool 
further  if  necessary,  stir,  and  then  pour  it  into  a  small  (No.  i) 
test-tube.    Is  a  homogeneous  solution  obtained? 

2.  Repeat,   using  fuming  sulfuric  acid.     Be  careful  when 
pouring  the  solution  into  water.    Do  so  drop  by  drop.    Pour 
upon  ice  if  possible.     (?) 

3.  Repeat,  using  cone,  nitric  acid.     (?) 

4.  To  i  cc.  of  a  very  dilute  solution  of  potassium  perman- 
ganate (just  rose  color)  add  several  drops  of  benzine.     Shake. 
(Do  not  use  a  cork  stopper.)    Do  you  notice  any  change? 

The  above  general  reactions  with  bromine,  sulfuric  acid,  nitric 
acid,  and  permanganate  are  given  not  only  for  showing  the 
inertness  of  the  paraffins,  but  also  for  laying  the  foundation  of  a 
general  comparison  of  the  properties  of  other  types  of  hydro- 
carbons as  shown  by  their  reactions  toward  these  same  reagents. 
•See  under  ethylene,  acetylene,  and  benzene. 

NOTES 

i.  The  benzine  used  in  the  above  tests  is  a  fraction  of  petroleum 
usually  taken  between  70°  and  80°.  It  must  not  be  confounded  with 
benzene,  C&H.Q,  which  boils  at  82°.  The  compounds  in  pure  benzine 
will  react  only  very  slowly  with  fuming  sulfuric  acid  and  the  sulfonic 
acids  formed  are,  like  most  sulfonic  acids,  soluble  in  water.  The 
ordinary  benzine  sometimes  contains  impurities,  probably  "un- 
saturated"  hydrocarbons  formed  in  the  large-scale  distillation,  and 
these  substances  are  rapidly  attacked  by  even  cone,  sulfuric  acid  and 
charred.  These  things  must  be  borne  in  mind  when  interpreting 
the  results  in  this  particular  case. 


LABORATORY  EXPERIMENTS  33 

Since  benzine  and  benzene  are  both  pronounced  the  same,  con- 
fusion as  to  which  is  meant  often  arises.  Therefore  it  has  been  well 
suggested  that  the  term  "benzolene,"  which  corresponds  to  the 
neighboring  fraction,  gasolene,  be  used  instead  of  "benzine." 

2.  Opening  sealed  bottles:     Wrap  a  towel  around  the  bottle, 
leaving  the  neck  exposed,  and  make  a  file  mark  on  the  neck.    Then 
melt  the  end  of  a  stirring  rod  in  the  flame  and  immediately  touch 
the  file  mark  with  the  melted  glass.    Generally  this  causes  the  glass 
tube  to  crack.    If  this  fails  the  end  of  the  neck  may  be  knocked  off 
with  a  sharp  blow  of  the  file.    In  any  case,  the  bottle  should  be  held 
over  a  casserole  or  beaker  so  that  if  the  bottle  is  cracked  the  con- 
tents will  do  no  damage.    The  fuming  ac  d  may  be  kept  for  a  short 
time  for  laboratory  use  in  a  small  glass-stoppered  bottle. 

3.  Opening   bromine   bottles:     The   glass   stoppers   in   bromine 
bottles  are  often  "  frozen"  and  are  difficult  to  remove.    If  the  method 
given  in  the  general  notes,  p.  4,  does  not  prove  effective,  the  neck 
of  the  bottle  must  be  broken  off.    Have  ready  a  funnel  large  enough 
to  hold  the  entire  bottle,  supported  in  a  stand,  and  another  bottle 
underneath  ready  to  receive  the  bromine,  all  set  near  the  draft  pipe. 
Make  a  file  mark  around  the  neck,  wrap  the  bottle  all  over  with  a 
towel,  and  while  it  is  securely  held  in  an  upright  position  strike  the 
top  a  sharp  blow  with  the  file  or  a  small  hammer.    Carefully  remove 
the  towel,  protect  the  hand  with  a  towel  or  glove,  and  pour  the 
contents  into  the  funnel.    Be  sure  that  you  hold  the  bottle  in  such  a 
way  that  the  bromine  will  not  run  down  on  your  fingers,  and  hold 
the  entire  bottle  over  the  funnel  in  order  that  none  will  run  outside 
See  p.  6  for  treatment  of  bromine  burns. 

QUESTIONS 

1.  What  is  the  purpose  of  the  copper  sulfate  solution? 

2.  Why  is  alcohol  added  to  the  mixture  of  zinc  dust,  etc.? 

3.  Why  is  the  first  test-tube  of  the  gas  discarded? 

4.  Why  is  carbon  tetrachloride  used  as  a  solvent  for  bromine 

in  these  tests  instead  of  water?  (Noyes  and  Mulliken, 
"Class  Reactions  and  Identification  of  Organic  Sub- 
stances," 3d  Ed.  (1915),  8.) 

5.  What  is  the  object  of  pouring  the  mixture  of  benzolene  and 

cone.  H2SO4  into  water?  (Compare  properties  of  sulfonic 
acids.)  Why  is  a  "small,  No.  i,  test-tube"  used? 

6.  Are  the  paraffins  ever  acted  upon  by  H2$O4  or 


34  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

7.  Give  two  other  general  methods  (applicable  to  the  entire 

paraffin  series)  of  forming  ethane. 

8.  Why  must  a  cork  stopper  not  be  used  when  making  the 

permanganate  test? 

9.  What  is  the  main  constituent  of  the  benzolene  used?   Could 

it  be  obtained  pure  by  fractional -distillation? 
10.  Why  does  the  gas  as  prepared  in  this  experiment  burn  with 
a  green  flame? 


Experiment  No.  6 

FORMATION    or    AN    ALKYL   HALIDE   BY   THE   REPLACEMENT 
OF  AN  ALCOHOLIC  HYDROXYL  GROUP  WITH  HALOGEN 

Preparation  of  Ethyl  Iodide  from  Ethyl  Alcohol 

To  2  grams  of  red  phosphorus  and  10  cc.  of  absolute  ethyl 
alcohol  in  a  glass-stoppered  bottle  add  in  small  quantities  17 
grams  of  powdered  iodine.  Shake  and  cool  if  necessary  after 
each  addition  by  immersion  in  water.  Stopper  the  bottle  and 
set  it  aside  for  twenty-four  hours  or  longer.  Then  transfer 
the  reaction-mixture  to  a  small  round-bottomed  flask,  rinse  out 
the  bottle  with  2-3  cc.  of  absolute  alcohol  and  add  the  rinsings 
to  the  main  solution.  Heat  under  a  reflux  condenser  on  the 
steam-bath  for  fifteen  minutes.  Then  cool  and  dry  the  out- 
side of  the  flask,  connect  with  a  straight  water  condenser  by 
means  of  a  bent  glass  tube,  and  distill1  with  care  (without  using 
a  thermometer)  until  no  more  liquid  passes  over.  The  mixture 
will  bump  somewhat  and  this  can  more  or  less  be  avoided  by 
keeping  the  flame  in  motion.  Put  the  distillate  into  a  Squibb 's 
separatory  funnel,2  add  some  water  and  test  with  litmus.  (?) 
Add  a  dilute  solution  of  sodium  hydroxide,3  stopper  securely 
and  agitate  gently  in  the  following  manner:  Invert  the  funnel, 
holding  the  stopper  in  with  one  hand  and  placing  the  thumb 

1  Use  a  small  flame.  Excessive  heat  may  decompose  the  phosphorous  acid 
formed  in  the  reaction,  giving  phosphine. 

-  2  Fig.  6.  When  in  use  the  stop-cock  should  be  greased  with  a  good  stop- 
cock lubricant.  Vaseline  may  be  used,  but  it  is  not  recommended,  since  it  is  too 
"thin"  and  has  no  "body."  Be  sure  to  clean  the  separatory  funnel  before  leaving 
the  laboratory,  so  that  the  stopper  and  the  stop-cock  will  not  stick.  It  is  well 
to  keep  the  ground  parts  separated  but  tied  with  a  piece  of  twine.  The  separatory 
funnel  is  conveniently  supported  in  a  ring  which  is  clamped  to  a  stand. 

3  Cold  dilute  sodium  hydroxide  solution  causes  no  appreciable  hydrolysis 
under  these  conditions. 

35 


36 


LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 


of  the  other  hand  on  the  handle  of  the  stop-cock  and  the  first 
two  fingers  on  the  other  side  of  the  stem,  and  shake.  While 
it  is  still  inverted  open  the  stop-cock  to  release  the  pressure. 
(?)  Repeat  both  these  operations  several  times.  Turn  the 
funnel  right  side  up,  support  it  in  a  ring  and  as  soon  as  the 
mixture  has  separated1  into  layers,  remove  the  upper  stopper, 
(Why?)  and  then  allow  the  heavy  lower  layer  of  ethyl  iodide 
to  flow  into  a  clean  beaker,  cutting  off  the  stream  when  the  upper 


SEPARATION FUNNEL 

(GLOBE.  SHAPE) 


SEPARATORY  FUNNEL 


FIG.  6. 


DROPPING 
FUNNEL 

,-NOTE    NARROW 
J  OUTLET     TUBE 


layer  flows  through  the  stop -cock.  The  ethyl  iodide  is  usually 
turbid  on  account  of  the  presence  of  water.  If  the  brown  color 
(?)  has  not  been  removed  and  if  the  aqueous  layer  is  not  alkaline, 
treat  it  with  a  second  portion  of  sodium  hydroxide  solution. 

1  Alkaline  solutions  sometimes  form  difficultly  separable  emulsions.  If  the 
separation  is  not  complete  within  an  hour  and  if  it  is  inconvenient  to  let  it  stand 
overnight,  add  dilute  acid  until  the  mixture  just  reacts  acid.  This  procedure 
will  usually  break  up  an  ordinary  emulsion. 


LABORATORY  EXPERIMENTS  37 

Separate  as  above.  Remove  any  water  from  the  stop-cock  and 
the  stem,  and  again  return  the  lower  layer  for  one  more  washing 
with  water.  This  time  make  a  very  careful  separation,1  allowing 
the  lower  layer  to  run  into  a  small  dry  Erlenmeyer  flask.  The 
liquid  still  contains  a  small  amount  of  water,  although  there 
may  not  be  enough  to  make  it  turbid.  This  last  trace  of  water 
is  removed  by  allowing  the  liquid  to  remain  in  contact  with 
a  good  drying  agent  such  as  calcium  ch  oride  for  several  hours, 
or  better  overnight.  Add  several  pieces  of  granular  anhydrous 
calcium  chloride,  stopper  the  flask,  (Why?)  and  set  aside  until 
the  next  laboratory  period.  The  Erlenmeyer  flask  is  used  in 
order  that  practically  all  the  liquid  may  be  in  close  proximity 
to  the  drying  agent.  Such  flask  should  never  be  more  than  half 
full.  For  a  discussion  of  drying  agents,  etc.,  see  Gattermann, 
"'  Practical  Methods  of  Organic  Chemistry,  3d  Amer.  Ed.,  pp. 
53-6;  and  Weyl,  "  Die  Methoden  der  Organischen  Chemie," 
II  (2)  (1911),  1357-64- 

When  the  liquid  is  clear  and  dry  filter  it  through  a  funnel, 
containing  a  small  plug  of  glass  wool  pushed  well  down  in  the 
stem,  into  a  small  dry  distilling  flask  (the  stem  of  the  funnel 
•  should  reach  below  the  opening  of  the  delivery  tube) ,  but  do  not 
I  allow  any  of  the  droplets  of  the  solution  of  calcium  chloride  that 
;  may  be  present  to  flow  into  the  flask  with  the  dry  ethyl  iodide. 
Distil]  through  a  water  condenser  with  a  straight  dry  inner  tube; 
using  a  dry,  weighed  specimen  bottle2  as  the  receiver.3     Ethyl 
iodide  boils  at  72°  cor.,  and  its  specific  gravity  is  1.994  (14°). 
Compounds  containing  a  halogen,  and  particularly  those  con- 
taining iodine,  have  a  tendency  to  decompose  on  strong  heating. 
Therefore  a  very  small  flame  should  be  used  in  this  instance, 
and  the  heating  should  not  be  continued  until  the  last  traces  are 
decomposed  because  some  of  the  products,  which  are  colored,  will 
pass  over  and  contaminate  the  pure  distillate.    Yield,  16  grams. 

1  If  drops  of  ethyl  iodide  float  on  the  water,  they  can  be  made  to  drop  to  the 
bottom  by  sudden  jars  to  break  the  surface  tension,  or  by  filling  the  funnel  with 
water,  thereby  lessening  the  area  of  the  upper  surface. 

2  See  p.  i. 

3  A  turbid  distillate  shows  the  presence  of  moisture.    It  must  be  dried  again 
1  over  night  with  fresh  calcium  chloride. 


38  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

§ 

What  is  the  corrected  boiling-point?  Calculate  the  theo- 
retical yield  on  the  basis  of  the  alcohol  used,  also  of  the  iodine, 
and  compare  with  the  actual  results.  What  is  the  percentage 
yield  on  each  basis?  The  product  becomes  dark  on  standing, 
especially  in  the  presence  of  light.  A  globule  of  mercury  placed 
in  the  bottle  will  keep  the  specimen  colorless.  (Why?) 

Bottle  the  product,  label  as  directed  in  the  "  Notes,"  p.  i, 
and  place  in  the  proper  tray  for  inspection  by  the  instructor. 

Before  handing  in  the  preparation  perform  the  following 
experiments : 

a.  Test  the  action  of  silver  nitrate  solution  on  a  drop  of, 
ethyl  iodide.     Is  there  an  immediate  precipitate?     Repeat  with 
chloroform.     (?) 

b.  Dissolve   i   gram  of  potassium  hydroxide  in   10  cc.  of 
alcohol.    Use  the  KOH  marked  "  purified  by  alcohol."  1    To 
i  cc.  of  this  solution,  which  is  commonly  known  as  "  alcoholic 
potash,"  add  nitric  acid  until  the  solution  reacts  acid,  and  then 
add  distilled  water  to  dissolve  any  precipitate.     (?)     To  this 
solution  add  a  drop  of  silver  nitrate  solution.     Is  there  any 
precipitate  or  is  the  solution  turbid?     (Why?) 

c.  Boil  i  cc.  of  "  alcoholic  potash  "  containing  one  drop  (no 
more)  of  ethyl  iodide  for  one  minute.     Cool  and  acidify  with 
nitric  acid,  dissolving  any  precipitate  (?)  with  distilled  water. 
If  an  emulsion  is  formed  add  alcohol,  or  repeat,  using  a  smaller 
amount  of  the  halide.     Then  add  a  drop  of  silver  nitrate  solution. 
Is  there  an  immediate  precipitate?    How  do  you  account  for  it? 

Reference  for  the  preparation  of  alkyl  iodides  in  large  quantities, 
Adams  and  Voorhees,  Journ.  Amer.  Chem.  Soc.,  41  (1919),  789-98. 

QUESTIONS 

1.  Could  yellow  phosphorus  be  used  in  preparing  ethyl  iodide? 

(See  reference  to  Adams  and  Voorhees,  p.  3 1 .) 

2.  Why  is  a  glass-stoppered  bottle  used? 

1  If  this  is  not  available,  dissolve  some  ordinary  stick  potassium  or  sodium 
hydroxide  in  absolute  alcohol  and  filter  from  any  chloride  or  carbonate.  Or  use 
a  solution  of  metallic  sodium  in  alcohol.  In  the  latter  case  only  clean  bright 
sodium  should  be  used,  the  parings  being  returned  to  the  bottle. 


LABORATORY  EXPERIMENTS  39 

3.  Why  is  absolute  alcohol  used? 

4.  Why  is  the  reaction  mixture  set  aside  overnight? 

5.  Why  is  the  bottle  rinsed  with  a  small  amount  of  alcohol? 

6.  Account  for  the  formation  of  the  hydrogen  iodide  which  is 

evidenced   by   the   cloud   of  vapor  when   the   reaction- 
mixture  is  transferred. 

7.  Why  is  a  thermometer  not  used  in  the  first  distillation? 
K.  When  is  fused  calcium  chloride  used  for  drying  liquids? 

9.  What  causes   the   "  brown  color  "?    How  is  it  removed? 
Write  the  reactions. 

10.  How  does  the  mercury  keep  the  specimen  colorless? 

11.  Give  two  other  methods  for  forming  ethyl  iodide. 

12.  Why  cannot  ethyl  iodide  be  prepared  by  the  direct  action  of 

iodine  on  ethane? 

13.  Compare  the  preparation  of  ethyl  iodide  and  of  hydrogen 

iodide. 

14.  Why  is  the  halogen  in  alkyl  halides  not  generally  precipi- 

tated with  silver  nitrate  solution? 

15.  What  is  the  qualitative  test  for  halide-ion  in  aqueous  solu- 

tion? 

1 6.  What  is  the  brown  precipitate  formed  when  not  enough 

nitric  acid  has  been  added  to  make  the  solution  react  acid? 

17.  What  would  happen  in  (c)  if  aqueous  potash  were  used? 

Try  it. 

18.  What  is  a  general  method  of  detecting  the  halogens  in  organic 

compounds?     Can  the  sodium-decomposition  be  used  if 
nitrogen  is  also  present?     Compare  Expt.  No.  28. 

19.  What  impurities  does  the  ordinary    potassium    hydroxide 

contain?    Acidify  a  dilute  solution  of  potassium  hydroxide 
with  nitric  acid  and  add  silver  nitrate  solution.     (?) 

20.  How  are  the  halogens  determined  quantitatively? 

21.  What  is  alkylation? 


Experiment  No.  7 

FORMATION  OF  AN  OLEFINE  HYDROCARBON 

AND 
ADDITION  OF  A  HALOGEN  TO  AN  OLEFINE  HYDROCARBON 

Preparation  of  Ethylene    (Ethene)   and    Ethylene    Dibromide 
(1.2-Dibrom-ethane) 

In  this  experiment  ethylene  is  prepared  by  heating  ethyl 
alcohol  and  phosphoric  acid,  and  the  ethylene  thus  made  is 
purified  by  passage  through  cone,  sulfuric  acid  and  then  run 
into  bromine,  which  absorbs  it  with  the  formation  of  ethylene 
dibromide.  After  the  ethylene  dibromide  is  made,  the  gas 
itself  is  collected  and  studied. 

Set  up  the  apparatus  shown  in  Fig.  7.    Use  rubber  stoppers. 

Care  must  be  exercised  in  putting  the  glass  tubes  through 
the  rubber  stoppers.  Be  sure  to  round  the  edges  of  all  tubes 
in  the  flame.  (See  p.  28.)  Use  a  drop  of  water  or  of  glycerine 
as  a  lubricant.  Always  take  hold  of  the  tube  near  the  stopper 
and  twist  it  slowly  as  it  is  carefully  being  forced  in.  Never, 
for  example,  grasp  a  long  thermometer  at  one  end  to  push  the 
other  end  through  the  stopper.  With  these  precautions  acci- 
dents resulting  in  more  or  less  serious  cuts  would  be  avoided. 

As  a  rule  it  is  not  necessary  to  enlarge  the  hole  in  a  rubber 
stopper.  In  case  a  larger  hole  is  required  a  cork  borer  can  be 
used.  It  must  be  moistened  frequently,  and  only  very  slight 
pressure  is  needed,  otherwise  a  tapering  hole  will  be  made. 

The  connections  with  rubber  tubing  are  easily  made  if  you 
breathe  through  the  rubber  tubing  before  pushing  it  over  the 
glass.  Here  again  the  sharp  edges  of  the  glass  tube  should  be 
well  rounded  in  the  flame. 

40 


LABORATORY  EXPERIMENTS 


41 


Fit  a  250  cc.,  round-bottomed,  short-necked  flask  with 
a  three-holed  stopper  through  which  pass  a  thermometer,  a  bent 
outlet  tube,  with  the  bend  near  the  stopper,1  and  an  inlet  tube 
drawn  into  a  narrow  tube,  1.5-2  mm.  in  diameter,  with  the 
lower  end  bent  upwards  about  5  mm.  The  size  of  this  tube 
is  important.  If  it  is  larger  or  smaller  than  designated  it  will 
not  deliver  the  alcohol  properly.  The  tapering  should  begin 


Diagram 
for  Efhylene   Di bromide 

FIG.  7. 

just  below  the  stopper  and  the  tube  should  extend  almost  to  the 
bottom  of  the  flask,  so  that  the  alcohol  can  be  delivered  well 
below  the  surface  of  the  liquid.  Turn  the  bend  away  from  the 
thermometer. 

1  The  apparatus  should  be  so  arranged  that  the  alcohol  which  condenses  below 
the  first  bend  in  the  outlet  tube  will  not  drip  upon  the  lower  part  of  the  ther- 
mometer and  cause  it  to  crack.  In  order  to  avoid  back  flow  of  any  condensation 
liquid  slant  the  outlet  tube  as  shown. 


42  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

To  make  the  inlet  tube,  heat  evenly  a  piece  of  glass  tubing 
held  lengthwise  in  the  flame  of  a  burner  provided  with  a  wing- 
top,  rotating  it  and  moving  it  from  left  to  right  until  it  becomes 
very  soft,  then  remove  it  from  the  flame  and  slowly  at  first  and 
then  much  more  rapidly  draw  it  out  as  desired.  Very  rapid 
drawing  makes  the  tube  too  narrow.  It  must  be  made  in  one 
heating.  A  smoky  flame  need  not  be  used  as  long  as  the  tube 
is  slowly  warmed  in  the  blue  flame.  The  narrow  tube  is  easily 
broken  where  a  file  mark  is  made.  It  is  bent  by  softening  the 
tube  near  the  end  in  the  flame  and  quickly  touching  the  end  to  a 
hard  surface  when  it  will  bend  very  readily.  Do  not  fuse  the 
capillary  or  change  its  bore. 

Connect  a  dropping-funnel  (Fig.  6)  with  rubber  tubing  to  the 
upper  part  of  the  inlet  tube  above  the  stopper,  and  wire  the  connec- 
tions.1 Lead  the  gas  (i)  through  an  empty  250  cc.  wide-mouthed 
bottle  as  a  safety  bottle,  using  a  three-holed  stopper.  The  three 
tubes  in  this  stopper  should  be  cut  off  just  below  the  stopper. 
Insert  a  glass  stop-cock  and  attach  a  piece  of  rubber  tubing  to 
lead  away  the  gases  to  the  draft  pipe.  From  this  bottle  lead  the 
gas  through  a  long  high  glass  tube  into  (2)  a  2  cm.  test-tube 
with  side  neck,  where  it  is  washed  by  passing  through  10  cc.  of 
cone,  sulfuric  acid.  This  test-tube  should  be  provided  with  an 
open  safety  tube  30  cm.  long  which  should  be  drawn  out  and  bent 
slightly  upwards  at  the  bottom,  opening  under  the  surface  of  the 
liquid.  The  long  high  connection  is  used  in  order  that  the 
operator  may  be  able  to  see  the  cone,  sulfuric  acid  rising  in  case 
of  back  pressure  in  the  apparatus  and  have  time  to  prevent  its 
being  drawn  into  the  first  bottle  by  equalizing  the  pressure 
by  opening  the  stop-cock  momentarily.  Then  (3)  through 
another  test-tube  with  side  neck  containing  7  cc.  of  bromine2 

1  This  rubber  connection  must  be  wired  since  the  rubber  absorbs  alcohol  and 
swells  so  much  that  the  joint  becomes  loose 

2  Not  bromine  water.    Do  not  add  the  bromine  until  just  before  the  experi- 
ment is  begun.    If  the  bromine  is  allowed  to  stand  in  the  tube  for  several  days 
before  the  experiment  is  begun  it  attacks  the  rubber  stopper.    Colored  compounds 
are  formed  which  run  down  the  walls  into  the  bromine.    Since  their  color  is  red  or 
reddish-brown  thsy  make  it  very  difficult  to  tell  when  all  the  bromine  is  decolor- 
ized with  the  ethylene.    Always  handle  bromine  near  the  draft  pipe  or  under 


LABORATORY  EXPERIMENTS  43 

covered  with  10  cc.  of  water.  The  two  tubes  leading  the  gas 
into  the  sulfuric  acid  and  into  the  bromine  should  be  drawn 
out  to  a  small  opening  so  that  the  issuing  bubbles  will  be  small. 
Both  tubes  should  open  near  the  bottom  of  the  test-tubes.  The 
two  test-tubes  can  conveniently  be  arranged  and  supported  on 
one  ring-stand.  Set  the  first  bottle  and  the  two  test-tubes  in 
beakers  full  of  cold  water.  Finally  (4)  through  a  tube  opening 
just  above  the  surface  of  a  normal  sodium  hydroxide  solution  con- 
tained in  a  bottle  provided  with  a  vent.  Or  the  bromine  vapors 
may  be  adsorbed  by  passing  the  gas  through  a  calcium  chloride 
tube  filled  with  adsorbent  charcoal.  In  either  case  lead  the  gases 
finally  into  the  draft  pipe. 

Into  the  generating  flask  put  a  mixture  of  40  cc.  of  syrupy 
phosphoric  acid  (sp.  gr.  1.7)  and  20  cc.  of  alcohol.  Almost  fill 
the  main  bulb  of  the  dropping-funnel  with  alcohol,  and  in 
order  to  displace  the  air  in  the  tube  allow  some  of  the  alcohol 
to  flow  into  the  flask.  Heat  the  flask  over  a  wire  gauze  until  the 
thermometer  in  the  mixture  indicates  230°.  Only  a  small 
flame  is  necessary  after  the  flask  is  heated  through.  During 
the  preliminary  heating  have  the  stop-cock  open.  When  the  evo- 
lution of  ethylene  has  well  begun  close  the  stop-cock,  and  let 
the  alcohol  run  in  slowly  at  such  a  rate  (about  one  drop  a  second) 
as  will  give  a  good  constant  stream  of  gas.  Keep  the  tempera- 
ture between  23o°-25o°.  Drafts  cool  the  flask  and  cause  such 
a  back  pressure  that  the  sulfuric  acid  and  bromine  may  be 
drawn  into  the  preceding  bottles.  This  back  flow  may  readily 
be  avoided  by  opening  the  s top-cock ,  as  mentioned  above. 
The  liquid  in  the  flask  should  appear  as  if  filled  with  bubbles 
and  will  foam  as  the  ethylene  is  regularly  generated.  The  tem- 
perature may  rise  even  above  250°  but  should  not  be  allowed  to 
reach  300°.  Continue  the  passage  of  the  gas  until  the  bromine 
has  changed  completely  to  a  straw-colored  liquid.  This  will 

the  hood.  If  you  get  any  on  your  hands  wash  it  off  immediately  with  alcohol, 
and  then  rub  in  some  carron  oil  (half  linseed  oil  and  half  lime  water)  or  carbolated 
vaseline.  Benzene  and  gasoline  are  good  solvents  and  may  also  be  used  for  remov- 
ing bromine.  See  p.  6. 

For  opening  bromine  bottles,  compare  Note  3,  under  Methane,  p.  33. 


44  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

take  about  thirty  minutes.  Much  more  time  will  be  necessary 
if  the  gas  is  not  delivered  near  the  bottom  where  it  will  stir 
up  the  bromine  and  be  more  readily  absorbed.  Purify  it  accord- 
ing to  the  directions  given  below. 


NOTES  ON  THE  GENERATION  OF  ETHYLENE 

1.  Be  sure  to  open  the  stop-cock  before  turning  out  the  flame. 

2.  The  generation  of  the  gas  may  be  stopped  and  resumed  at 
any  time. 

3.  When  carrying  out  this  experiment  it  is  well  to  protect  the 
eyes  with  goggles. 

4.  Do  not  try  to  burn  the  gas  leaving  the  apparatus  unless  the 
end  of  the  delivery  tube  is  drawn  into  a  capillary  opening.     (Why?) 

5.  The  method  can  be  used  for  preparing  fairly  large  quantities 
of  ethylene.     However,  the  phosphoric  acid  attacks  the  glass  and 
after  about  16-20  hours  running  the  inlet  tube  is  generally  "eaten 
off"  and  finally  the  flask  itself  will  leak. 

After  the  color  of  the  bromine  has  disappeared  disconnect  the 
second  test-tube,  connect  the  outlet  tube  of  the  sulfuric  acid  tube 
with  a  tube  leading  to  a  beaker  or  small  pail  of  water,  and  when  a 
test-tube  of  the  gas  collected  over  water  burns  quietly  fill  two 
250  cc.  narrow-necked,  glass-stoppered  bottles  and  a  250  cc. 
ordinary  wide-mouthed  bottle  with  the  gas  by  displacement. 

a.  Into  one  narrow-necked  bottle  pour  i  cc.  of  bromine  water. 
Insert  the  glass  stopper  immediately  and  shake.     (?) 

b.  To  the  second  narrow-necked  bottle  add  i  cc.  of  a  very 
dilute  solution  of  potassium  permanganate.1     Close  with  the 
glass  stopper  and  shake  vigorously.     (?) 

c.  Ignite  the  gas  in  the  wide-mouthed  bottle  (near  the  draft 
pipe)  and  immediately  add  water  to  displace  the  gas.     Is  the 
flame  distinctly  luminous? 

Repeat  the  above  experiments  using  city  gas.  Conclusions.  (?) 

1  For  the  oxidation  of  ethylene,  see  Stoddard,  "Introduction  to  Organic  Chem- 
istry," p.  156;  of  other  defines,  see  Moore,  "Outlines  of  Organic  Chemistry," 
2nd  Ed.,  p.  129. 


LABORATORY  EXPERIMENTS  45 

Test  amylene  or  pinene  for  the  " double  bond"  as  follows: 
Use  i  cc.  in  each  case. 

a.  Add  i  drop  of  cone,  sulfuric  acid.     (Care!)     Result? 

b.  Add  i  drop  of  cone,  nitric  acid.     (Care!)     Result? 

c.  Add  a  solution  of  bromine  in  carbon  tetrachloride.     (?) 

d.  Add  i  cc.  of  potassium  permanganate  solution  as  above 
and  shake.     (Do  not  use  a  cork  stopper.) 

Compare  the  results  with  those  obtained  with  benzine. 
(Expt.  No.  5,  p.  31.) 

Transfer  the  crude  ethylene  dibromide  to  a  Squibb 's  separa- 
tory  funnel:  add  some  dilute  sodium  hydroxide  solution,  agitate 
gently,  and  separate.1  Return  the  heavy  liquid  to  the  separatory 
funnel,  and  treat  again  with  a  dilute  solution  of  sodium  liy- 
droxide  unless  the  aqueous  layer  remained  alkaline  in  reaction. 
Finally  wash  once  with  water,  and  draw  off  into  a  dry  Erlenmeyer 
flask.  The  product  may  be  slightly  colored.  This  is  due  to  the 
fact  that  some  decomposition  took  place  on  account  of  the  heat 
of  the  reaction  between  the  ethylene  and  bromine  with  the 
formation  of  a  small  amount  of  colored  by-products.  This  color 
cannot  be  removed  with  alkali.  Add  several  pieces  of  calcium 
chloride  to  the  cloudy  ethylene  dibromide,  cork  the  flask  (?), 
and  set  aside  for  several  hours  (overnight)  to  dry  the  liquid. 
Filter  through  a  funnel  containing  a  plug  of  glass  wool  in  the 
stem  into  a  dry  distilling  flask,  just  as  in  the  ethyl  iodide  experi- 
ment, but  do  not  allow  any  of  the  droplets  of  the  calcium  chloride 
solution2  that  may  be  present  to  flow  into  the  flask  with  the  dry 
ethylene  dibromide.  (Why?)  Distill  through  a  water  condenser 
with  dry  inner  tube,  using  a  dry-weighed  specimen  bottle  as  the 
receiver,  observing  the  precautions  mentioned  under  ethyl 
iodide.  The  substance  boils  at  131.2°  cor.,  melts  at  9.5°,  and 
its  specific  gravity  is  2.1774  (2i°/4°)-  Yield,  20  grams.  Cal- 

1  For  separating  an  emulsion,  see  foot-note,  p.  36. 

2  If  there  is  a  layer  of  calcium  chloride  solution,  even  though  some  of  the  solid 
is  still  present,  it  is  quite  probable  that  the  product  is  not  very  dry.    It  should 
be  separated,  treated  with  fresh  calcium  chloride,  and  allowed  to  stand  for  several 
hours  longer, 


46  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

culate  the  theoretical  yield  from  the  amount  of  bromine  used. 
What  is  your  corrected  observed  boiling-point? 

Repeat  tests  a  and  c  as  given  under  ethyl  iodide  (p.  38),  with 
pure  ethylene  dibromide,  and  compare  the  results  with  those  ob- 
tained with  ethyl  iodide.  Write  the  equations. 


NOTE  ON  TAKING  APART  THE  APPARATUS 

The  glass  tubes  often  stick  in  the  rubber  stoppers.  In  such  cases 
do  not  try  to  pull  out  the  tube  directly.  Work  the  rubber  away  from 
the  tube  with  the  fingers  and  allow  water  to  flow  in  and  moisten  it 
as  fast  as  it  is  separated.  In  this  manner  the  tube  soon  becomes  free 
and  can  be  withdrawn  easily. 

QUESTIONS 

1.  What  objection  is  there  to  an  inlet  tube  with  a  diameter 

less  than  2  mm.?  Greater  than  2  mm.? 

2.  Why  must  the  alcohol  be  delivered  below  the  surface  of  the 

liquid?     Why  is  the  inlet  tube  turned  up  at  the  bottom? 

3.  What  substances  are  caught  in  the  empty  safety  bottle? 

Account   for   them.     Is   this   the   only   purpose   of   this 
bottle? 

4.  Why  must  the  gas  be  passed  through  cone.  H2S04?    Could 

fuming  H2SO4  be  used?  dilute  H2SO4? 

5.  Why  should  the  alcohol  vapors  not  be  allowed  to  go  over 

into  the  bromine? 

6.  Why  are  the  bottles  surrounded  with  cold  water? 

7.  Why  is  the  bromine  covered  with  a  layer  of  water? 

8.  What  substances  are  caught  in  the  sodium  hydroxide  solu- 

tion?   Account  for  them. 

9.  Why  is  the  apparatus  disconnected  before  extinguishing  the 

flame? 

10.  What  is  the  brown  precipitate  formed  in  the  permanganate 

test? 

11.  What  unsaturated  hydrocarbons  are  in  the  city  gas?    What 

are  illuminants?    Name  some. 

12.  How  are  the  unsaturated  hydrocarbons  in  illuminating  gas 

estimated? 

13.  Is  an  addition  or  substitution  product  formed  with  amylene 

and  sulfuric  acid? 


LABORATORY  EXPERIMENTS  47 

14.  In  the  purification  of  ethylene  dibromide  why  must  the 

sodium  hydroxide  solution  be  used? 

15.  Why  avoid  the  emulsion  which  would  be  formed  by  vigorous 

shaking? 

1 6.  Why  is  a  250  cc.  Squibb 's  separatory  funnel  used  instead  of  a 

dropping-funnel  although  the  volume  of  liquid  is  small? 
(Fig.  6,  p.  36.) 

17.  Why  not  dry  the  product  in  a  small  distilling  flask  and 

distill  directly  without  removing  the  calcium  chloride? 

18.  Why  is  glass  wool  used  instead  of  a  filter  paper  in  the 

funnel? 

19.  What  compounds  are  in  the  "  amylene  "? 

20.  Look  up  the  formula  for  pinene. 

21.  Why  not  use  the  weight  of  the  alcohol  instead  of  the  bro- 

mine in  calculating  the  theoretical  yield? 

22.  Is  ethylene  dibromide  a  saturated  or  unsaturated  compound? 

Of  what  hydrocarbon  is  it  a  derivative? 

23.  What  happens  when  ethylene  dibromide  is  heated  with  alco- 

holic sodium  hydroxide?      Vith  aqueous  sodium  hydroxide? 

24.  What  other  methods  can  be  used  for  preparing  ethylene? 

25.  How  did  the  United  States  Government  prepare  ethylene  in 

large  quantities  for  the  manufacture  of  "  mustard  gas  " 

t(dichlor-diethyl-sulfide)  during  the  war?     (Ref.,  Dorsey, 
Journ.  Ind.  and  Eng.  Chem.,  11  (1919),  288. 


Experiment  No.  8 

FORMATION  OF  AN  OLEFINE  HYDROCARBON 
Ethylene  from  Ethyl  Alcohol  (for  Short  Course) 

Weigh  directly  into  a  large  test-tube  (No.  3),  4  grams  of 
phosphorus  pentoxide.  Connect  the  test-tube  by  means  of  a 
closely  fitting  cork  with  a  reflux  air  condenser;  immerse  the  tube 
in  cold  water,  and  pour  5  cc.  of  ethyl  alcohol  slowly  through  the 
condenser.  The  alcohol  should  be  added  cautiously  in  small 
portions  and  the  test-tube  shaken  under  water,  since  much  heat 
is  evolved  when  alcohol  comes  in  contact  with  phosphorus 
pentoxide.  Remove  the  condenser,  support  the  test-tube  at  an 
angle  of  about  45°  with  the  desk  top  by  means  of  a  clamp,  and 
connect  it  with  a  delivery  tube  arranged  to  collect  gas  over 
water.  Heat  the  tube  carefully  until  the  mixture  becomes 
homogeneous;  then  more  strongly  until  a  steady  stream  of  gas 
is  evolved.  Fill  two  250  cc.  narrow-necked  glass-stoppered 
bottles  and  a  250  cc.  wide-mouthed  bottle  with  the  gas  over 
water  by  displacement. 

a.  Into  one  narrow-necked  bottle  pour  i  cc.  of  bromine  water. 
Insert  the  glass  stopper  immediately  and  shake.      (?) 

b.  To  the  second  narrow-necked  bottle  add  i  cc.  of  a  very 
dilute  solution  of  potassium  permanganate.     Close  with   the 
glass  stopper  and  shake  vigorously.     (?) 

c.  Ignite  the  gas  in  the  wide-mouthed  bottle   (near  the  draft 
pipe)  and  immediately  add  water  to  displace   the  gas.     Is  the 
flame  distinctly  luminous? 

Repeat  the  above  experiments,  using  city  gas.  Conclusions.  (?) 
Test  amylene  or  pinene  for  the  "  double  bond  "  as  follows: 
Use  i  cc.  in  each  case. 

a.  Add  i  drop  of  cone,  sulfuric  acid.     (Care!)     Result? 

48 


LABORATORY  EXPERIMENTS  49 

b.  Add  i  drop  of  cone,  nitric  acid.     (Care!)     Result? 

c.  Add  a  solution  of  bromine  in  carbon  tetrachloride.     (?) 

d.  Add  i  cc.  of  potassium  permanganate  solution  as  above 
and  shake.     (Do  not  use  a  cork  stopper.) 

Compare   the   results   with   those   obtained   with    benzine, 
Expt.  No.  5.,  p.  31. 

QUESTIONS 

i.  Compare  the  action  of  ethyl  alcohol  with  that  of  water  on 
phosphorus  pentoxide.  Write  structural  formulas  of  the 
compounds  in  each  case  and  name  them. 

2.  What  is  the  action  of  heat  on  the  compounds  formed  by  the 

action  of  ethyl  alcohol  and  of  water,   respectively,  on 
phosphorus  pentoxide? 

3.  Write  the  equation  for  the  reaction  of  bromine  and  ethylene. 

4.  What  happens  when  ethylene  is  treated  with  dilute  potassium 

permanganate? 

5.  What  is  the  brownish  precipitate  formed  in  the  perman- 

ganate test? 

6.  Define  an  addition  product;   a  substitution  product.     Illus- 

trate. 

7.  Is  ethylene  dibromide  a  saturated  or  an  unsaturated  com- 

pound?    Of  what  hydrocarbon  is  it  a  derivative? 

8.  Is  an  addition  or  substitution  product  formed  with  amylene 

and  sulfuric  acid? 

9.  What  unsaturated  hydrocarbons  are  in  the  city  gas? 

10.  What  are  "  illuminants  "?     Name  some. 

11.  How  are  the  unsaturated  hydrocarbons  in  illuminating  gas 

estimated? 


Experiment  No.  9 

FORMATION  OF  AN  ACETYLENE:     i.  BY  HYDROLYSIS  OF  AN 

ACETYLIDE 

Acetylene  from  Calcium  Carbide 

Set  up  a  gas  generator  consisting  of  a  filtering-flask  and 
dropping-funnel.  Into  the  dry  flask  place  several  lumps 1  of 
calcium  carbide  and  allow  water  to  drop  very  slowly  upon  it. 
(Care!)  Pass  the  gas  through  an  empty  safety-bottle  and  then 
fill  with,  the  gas  by  displacement  over  water  a  test-tube,  two 
narrow-necked  glass-stoppered  bottles,  and  a  wide-mouthed 
bottle  in  the  order  named. 

a.  Ignite  the  gas  in  the  wide-mouthed  bottle,  holding  it  near 
the  draft  pipe.     Notice  the  luminosity  of   the  flame  and  the 
amount  of  carbon  deposited. 

b.  To  one  narrow-necked  bottle  add  2  cc.  of  bromine  water 
and  shake.     (?)     Compare  with  methane,  p.  31,  and  ethylene, 
p.  44  or  p.  48. 

c.  To  the  other  narrow-necked  bottle  add  i  cc.  of  a  very 
dilute  solution  of  potassium  permanganate.     Shake.     Are  there 
any  signs  to  denote  unsaturation? 

d.  Dilute  0.5  cc.  of  silver  nitrate  solution  to  about  3  cc. 
From  a  test-tube  add  this  silver  nitrate  solution  to  a  test-tube 
of  the  gas.    What  is  the  white  precipitate?    Filter  with  suction 
and  let  it  dry  on  filter  paper.     Explode  it  by  heating  small  pieces 
in  the  flame.2    Note  the  presence  of  carbon  on  the  knife  blade 
after  the  explosion. 

e.  Prepare  a  solution  of  cuprous  chloride  as  follows:    Dis- 
solve 0.5  gram  of  copper  sulfate  crystals  in  a  little  water",  a^dd 

1  The  powder  is  generally  useless  since  it  is  mostly  decomposed. 

2  Destroy  all  the  remaining  silver  precipitates  before  leaving  the  laboratory, 
either  by  explosion  or  by  warming  with  dilute  hydrochloric  acid. 

50 


LABORATORY  EXPERIMENTS 


51 


2  cc.  of  cone,  ammonium  hydroxide  and  1.5  gram  of  hydroxyk- 
amine  hydrochloride.  Dilute  with  water  to  about  25  cc.  It  may 
be  kept  colorless  by  placing  it  in  a  tightly  corked  bottle  con- 


taining  some  copper  turnings.  The  bottle  should  be  full  in  order 
to  avoid  oxidation  by  any  air  present.  This  will  be  used  in  both 
parts  of  this  experiment. 

Pass  acetylene  into  5  cc.  of  the  cuprous  chloride  solution. 
What  is   the   reddish-brown  precipitate?    Filter   the   solution 


52  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

with  suction  and  wash  the  precipitate.  Let  it  dry  on  the  filtei 
paper,  and  then  explode  small  portions  of  it  in  the  flame  Try 
its  solubility  in  dilute  hydrochloric  acid  solution. 

Filtration  with  Suction. — In  order  to  filter  with  suction  fit  the 
porcelain  Buchner  funnel,  Fig.  8,  p.  51,  tightly  into  the  neck  of  a 
filtering-flask  with  a  good  cork  or  rubber  stopper,  and  connect 
the  outlet  tube  to  the  filter  pump  with  heavy  rubber  tubing. 
In  the  bottom  of  the  funnel  place  a  filter  paper  cut  so  that  it 
covers  all  the  holes  and  lies  flat  without  being  folded  on  the  sides. 
Moisten  the  paper  with  some  of  the  liquid  used,  start  the  suction, 
and  then  pour  in  the  mixture.  Oftentimes  with  bulky  material 
it  is  convenient  to  press  it  down  with  a  flat-topped  glass  stopper. 
At  the  end  of  the  filtration  carefully  disconnect  the  tube  from  the 
flask  before  stopping  the  suction. 

For  the  filtration  of  small  quantities,  see  p.  56. 

2.    BY  THE  ACTION  OF  ALCOHOLIC  POTASSIUM  HYDROXIDE  ON 
AN  ALKYLENE  DIHALIDE 

Acetylene  from  Ethylene  Dibromide 

To  a  100  cc.  flask  set  on  the  steam-bath  attach  an  addition 
tube  with  reflux  condenser  connected  with  its  side  opening.1 
From  the  top  of  the  condenser  run  a  tube  leading  into  5  cc. 
of  the  ammoniacal  cuprous  chloride  solution.  Have  all  con- 
nections tight.  Good  corks,  well  bored,  must  be  used.  Col- 
lodion sometimes  may  be  used  to  aid  in  making'  a  cork  gas- 
tight,  but  it  is  not  a  substitute  for  an  evenly  bored  cork.  Rubber 
stoppers  may  also  be  used  if  desired.  Heat  2  grams  of  potassium 
hydroxide,  "  purified  by  alcohol,"2  in  12  cc.  of  alcohol  in  the  flask 
for  about  ten  minutes.  Cool  and  add  through  the  addition 
tube  2  cc.  of  ethylene  dibromide.  Heat  again.  What  is  the 
precipitate  formed  in  the  cuprous  chloride  solution?  At  the  end 
of  the  reaction  dissolve  the  precipitate  (?)  in  the  flask  by  adding 
some  distilled  water,  add  nitric  acid  to  a  small  portion  of  this 

1  See  Fig.  3,  p.  13. 

2  Or  use  an  equivalent  amount  of  metallic  sodium  in  alcohol.     Connect  the 
condenser  to  the  flask  after  the  sodium  is  added,  since  the  alcohol  becomes  hot 
and  hydrogen  is  given  off. 


LABORATORY  EXPERIMENTS  53 

until  it  reacts  acid,  and  then  add  a  drop  of  silver  nitrate  solution. 
What  is  the  precipitate?     Account  for  it. 

NOTE 

Only  a  small  amount  of  the  ethylene  dibromide  is  converted  into 
acetylene.  The  major  portion  is  converted  into  vinyl  bromide  (mono- 
brom-ethylene)  which  is  a  gas  at  room  temperature  and  passes  out 
of  the  reaction  mixture  before  it  can  be  reacted  upon  further  and 
completely  transformed  into  acetylene.  If  no  acetylene  is  detected 
!  in  your  experiment  it  is  because  there  were  leaks  in  your  apparatus. 
Some  is  always  formed.  ^  H  ^ 

QUESTIONS 

1 .  What  two  compounds  may  be  formed  when  acetylene  and  p  \  -V  (^ 

bromine  react? 

2.  What  happens  when  an  acetylide  is  boiled  with  dil.  hydro- 

chloric acid? 

3.  What  kind  of  a  reaction  is  the  decomposition  of  calcium 

carbide? 

4.  What  causes  the  bad  odor  of  the  gas?     Source? 

5.  What  style  of  acetylene  hydrocarbons  form  metallic  deriv- 

atives? 

6.  When  the  copper  sulfate  is   reduced  to  the  cuprous  form, 

what  becomes  of  the  hydroxylamine? 

7.  Why  is  an  ammoniacal  solution  of  cuprous  chloride  used? 

8.  Why  is  ammonium  hydroxide  not  used  also  with  the  silver 

nitrate? 

9.  Are  all  acetylides  explosive? 

10.  What  is  meant  by  an  exothermic  compound?  an  endothermic 

compound? 

11.  Write  the  reactions  for  the  formation  of  acetylene  from 

ethylene  dibromide,  giving  the  different  products  formed. 

12.  Explain  why  the  acetylene  burns  with  a  smoky  flame  in 

the  experiment,  while  in  certain  lamps,  such  as  automo- 
bile lamps,  it  burns  with  an  exceedingly  bright  flame. 

13.  Discuss   the   reactions,  in   the   treatment   of   the    residual 

"  alcoholic  potash  "  solution. 

14.  What  advantages  has  a  Buchner  funnel  over  the  ordi'nary 

funnel? 

15.  In  the  suction  nitration  why  is  the  tube  disconnected  from 

the  flask  before  the  water  is  turned  off? 

16.  Why  should  the  filter  paper  not  be  allowed  to  "  run  up  '  • 

the  sides  of  the  Buchner  funnel? 


Experiment  No.  10 
Alcohols,  Reactions  of 

a.  Add  a  small  piece  of  bright  sodium  to  2  cc.  of  ethyl  alcohol. 
What  gas  is  evolved?    What  is  the  white  solid  that  separates 
as  the  solution  cools?    Add  more  sodium  if  nothing  separates  the 
first  time.     Is  this  reaction  characteristic  of  all  alcohols?    How 
do  you  name  the  compounds  formed? 

b.  Add  a  few  drops  of  cone,  sulfuric  acid  to  0.5  cc.  of  glacial 
acetic  acid  and  i  cc.  of  ethyl  alcohol.     Warm,  with  shaking. 
Pour  it  on  a  large  cover  glass  and  neutralize  with  sodium  car- 
bonate.    To  what  is  the  pleasant  odor  due?    To  what  class  of 
organic  compounds  does  it  belong?  •  -^ 

Repeat,  using  iso-amyl  alcohol.     (This  alcohol  usually  pro- 
duces coughing  when  breathed.) 

c.  Make  a  dilute  solution  of  sodium  dichromate,  add  a  drop 
or  two  of  cone,  sulfuric  acid  and  then  several  drops  of  ethyl 
alcohol.     Heat.     Notice    the    odor    of    the    vapors.    What   is 
formed?    What  causes  the  green  coloration? 


54 


Experiment  No.  11 

THE  IDENTIFICATION  OF  AN  ALCOHOL 
The  Methyl  Ester  of  3.5-Dinitrobenzoic  Acid 

It  is  seldom  possible  to  identify  organic  substances  in  the  same 
general  manner  as  inorganic  substances.  Class  reactions 1 
are  relied  upon  to  tell  the  nature  of  the  substance,  that  is,  its 
class,  such  as  a  hydrocarbon,  an  alcohol,  etc.,  and  physical  con- 
stants will  often  show  what  member  of  the  class  the  substance  is. 
Then,  in  order  to  make  certain,  the  substance  is  transformed  into 
a  derivative  which  can  readily  be  prepared  on  a  small  scale,  and 
a  physical  constant  taken  upon  this.  On  account  of  the  diffi- 
culties in  purifying  liquids  in  small  amounts,2  a  solid  derivative 
is  chosen  whenever  possible.  The  following  experiment  illus- 
trates this  point  in  the  case  of  the  lower  alcohols. 

In  a  small  dry  test-tube  heat  together  0.3  gram  of  3.5-dinitro- 
benzoic  acid  and  0.4  gram  of  phosphorus  pentachloride  over 
a  low  flame.  Keep  the  tube  in  motion  and  finally  allow  the 
mixture  to  boil  gently  for  a  minute.  Then  while  it  is  still 
liquid  pour  the  product  upon  a  small  dry  watch  glass.  When  the 
acid  chloride  (?)  has  solidified  remove  the  liquid  by-product, 
phosphorus  oxychloride,  adhering  to  it,  by  pressing  out  the 

1  Noyes  and  Mulliken,  "  Class  Reactions  and  Identification  of  Organic  Sub- 
stances," and  Clarke,  "A  Handbook  of  Organic  Analysis."    For  a  more  extended 
work,  see  the  three  monumental  volumes  by  Mulliken,  "Identification  of  Pure 
Organic  Compounds." 

2  For  a  method  of  determining  the  boiling-point  of  a  very  small  amount  of 
liquid,  see  Mulliken,  Vol.  I,  p.  222;  also  Alex.  Smith  and  Menzies,  Journ.  Amer. 
Chem.  Soc.,  32  (1910),  897. 

55 


56  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

mixture  with  a  porcelain  spatula 1  on  the  smooth  side  of  a  piece 
of  clean  porous  tile.2 

Put  the  dry  material  into  another  small  test-tube,  add 
eight  drops  of  methyl  alcohol,  stopper  the  tube  and  shake 
now  and  then.  The  reaction  is  soon  complete  and  after  a  few 
minutes  the  ester  can  be  recrystallized.  To  do  this,  place  the 
product  into  a  60  cc.  flask  under  a  reflux  condenser,  add  20  cc. 
of  dilute  alcohol  (3  volumes  of  alcohol  and  i  of  water),  and  heat 
to  boiling  by  heating  on  the  steam-bath  or  by  immersing  the  flask 
in  hot  water.  If  the  substance  does  not  completely  dissolve  after 
a  short  time  add  a  little  more  dilute  alcohol  and  boil  again. 
There  may  be  some  foreign  particles  which  will  not  go  into  solu- 
tion. Filter  the  hot  solution  through  a  small  filter  paper  into  a 
beaker  and  allow  the  filtrate  to  cool.  The  ester  crystallizes  in 
shining  leaflets.  Separate  these  by  filtering  with  suction. 

Filtration  of  Small  Quantities  with  Suction.  Use  a  Gooch 
perforated  porcelain  plate  in  a  No.  i  funnel,  and  place  upon 
the  plate  a  piece  of  filter  paper  just  large  enough  to  cover  it 
and  extend  to  the  walls  of  the  funnel.  Fasten  the  funnel  in  a 
stopper  in  the  neck  of  a  test  tube  with  side  opening.  Moisten 
the  filter  paper  with  dilute  alcohol,  start  the  suction,  and  proceed 
as  usual.  (See  Fig.  8,  p.  52,  and  compare  p.  52.) 

Allow  the  crystals  to  dry  between  filter  papers  or  under 
a  watch  glass  on  a  porous  tile,  and  then  determine  the  melting- 
point  according  to  the  directions  given  in  Expt.  No.  12,  p.  58. 
The  pure  substance  melts  at  107°  (uncor.). 

Other  esters3  of  this  acid  may  be  employed  to  identify  the 
corresponding  alcohols.  They  may  be  prepared  according  to 
the  directions  given  above  for  the  methyl  ester.  The  ethyl 
ester  melts  at  g2°-^°,  i°-propyl  ester,  73°;  i °-normal-butyl 
ester,  64°;  i°-iso-butyl  ester,  83°-84°. 

1  In  ordinary  cases  where  no  corrosive  substance  is  present  a  steel  spatula  can 
be  used.    It  should  be  cleaned  previously  with  soap  to  remove  traces  of  rust  and 
dirt. 

2  A  porous  unglazed  tile  is  good  for  one  drying,  unless  only  a  portion  of  the 
surface  has  been  used.    Obviously  it  cannot  be  washed. 

3Mulliken,  " Identification  of  Pure  Organic  Compounds,"  Vol.  I  (1904), 
168-72. 


LABORATORY  EXPERIMENTS  57 


QUESTIONS 

1.  Why  is  the  solid  ester  of  3.5-dinitrobenzoic  acid  made  for 

the  identification  of  an  alcohol  instead  of  the  liquid  ester, 
for  example,  of  acetic  acid? 

2.  Write  the  equations  for  the  reactions  for  preparing  the  methyl 

ester.  (Compare  Stoddard,  "  Introduction  to  Organic 
Chemistry,  2d  Ed.  (1918),  p.  354,  last  paragraph,  and 
p.  99,  No.  3,  near  bottom  of  the  page,  p.  114,  No.  2  and 
p.  116,  No  3.) 

3.  What  is  the  object  of  the  porous  tile?    Why  not  use  filter 

paper? 


Experiment  No.  12 
Determination  of  the  Melting-point 1 

The  melting-point  is  the  physical  property  most  generally 
used  as  a  criterion  of  the  purity  of  a  solid  organic  compound. 
It  also  serves  for  the  characterization  and  recognition  of  a 
compound.  On  account  of  its  significance  the  melting-point 
should  be  very  carefully  and  accurately  determined.  The  method 
employed  is  to  heat  a  small  amount  of  the  substance  in  a  capillary 
tube  attached  to  a  thermometer  in  a  suitable  bath  until  the  sub- 
stance becomes  a  clear  liquid  2  and  the  temperature  at  this  point 
is  recorded  as  the  melting-point.  A  substance  is  regarded  as 
pure  when  it  melts  within  0.2-0.4  of  a  degree,3  provided  that  the 
temperature  is  kept  as  nearly  constant  as  possible,  and  if  after 
repeated  crystallization  it  does  not  change.  Slow  melting 
over  several  degrees  usually  indicates  an  impure  compound, 
provided  the  rate  of  heating  is  all  right.  Some  pure  substances, 
however,  especially  those  of  high  molecular  weight,  do  not  show 
a  sharp  melting-point  in  the  ordinary  method  (compare  phenyl- 
glucosazone,  Expt.  34,  p.  129). 

Set  up  a  melting-point  apparatus  like  the  one  illustrated  in 
Fig.  9.  It  consists  of  two  tubes,  one  inside  the  other.  The  outer 
one  is  32  mm.  in  diameter  and  about  14.5  cm.  long;4  the  inner 
one  is  17  mm.  in  diameter  and  14  cm.  long,  and  has  a  series  of 

1  See  G.  A.  Menge,  "A  Study  of  Melting-point  Determinations,"  U.  S.  Hygienic 
Laboratory  Bulletin,  70  (1910),  for  an  excellent  description  and  discussion  of  the 
methods  of  determining  melting-points,  common  errors,  etc.    NOTE:  This  bulletin 
is  out  of  print,  but  may  be  consulted  in  the  general  library. 

2  Frequently  the  temperature  of  decomposition  (often  coincident    with   the 
melting-point)  is  taken,  but  in  this  case  there  is  the  possibility  of  a  greater  amount 
of  divergence  due  to  manipulation. 

3  This  error  is  about  equal  to  the  error  of  observation. 

4  The  outer  tube  of  a  Beckmann  freezing-point  apparatus  is  suitable. 

58 


LABORATORY  EXPERIMENTS 


small  holes  1  not  over  2  mm.  in  diameter — four  at  each  height — 
as  indicated  in  the  figure.  In  order  that  the  behavior  of  the  sub- 
stance can  be  watched  there  are  no  holes  opposite  the  bulb  of 


e 

1 

1 

i 

1 

1 

i 

f- 

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H2O  HOLES 
2  MM.  DM  M. 

c. 

) 

^ 

O"*- 

R 

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^ 

\ 

Q 

o 

IT 

\ 

s 

t 

1, 

o 

0 

MELTING-POINT 

^  —  - 

->• 

TUBE  

k. 

CONC.  H~SO*- 

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MELTING- POINT 

FIG.  9. 


the  thermometer.     The  inner  tube  can  be  supported  in  the  outer 
tube  by  means  of  a  cork  as  shown,  with  a  narrow  channel  cut 

1  In  case  an  inner  tube  all  perforated  is  not  at  hand,  the  holes  can  be  blown  in 
as  follows:  Select  a  test-tube  of  the  proper  dimensions,  stopper  it  with  a  good 
cork  which  carries  a  glass  tube  to  which  is  connected  a  piece  of  rubber  tubing 
for  blowing.  Heat  a  tiny  area  of  the  glass  at  the  desired  point  with  a  fine  blast 


60  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

along  the  edge  to  allow  the  heated  vapors  to  escape,  or,  when  the 
thermometer  is  in  position  and  securely  held  in  alignment  by  a 
cork,1  it  can  be  supported  by  holding  the  top  of  the  thermometer 
in  a  clamp. 

The  outer  tube  should  be  supported  by  clamping  it  firmly  but 
not  too  tightly  under  the  lip.  Add  enough  cone,  sulfuric  acid 
to  come  up  to  a  height  of  6  cm.  from  the  bottom  of  the  inner 
tube  when  it  is  in  place.2  The  apparatus  is  heated  with  a  small 
flame  which  should  be  protected  with  a  metal  chimney.  The 
liquid  in  the  inner  tube  is  regularly  heated  and  stirred  mainly 
by  means  of  convection  currents  made  possible  by  the  series  of 
small  holes.  The  liquid  near  the  thermometer  always  shows  an 
even  downward  flow  all  around  the  stem.3  Moreover,  the  inner 
liquid  can  be  heated  uniformly  and  steadily  since  it  is  not  affected 
by  ordinary  drafts. 

Make  several  capillary  tubes,  the  so-called  melting-point 
tubes,  as  follows:  Heat  evenly  a  piece  of  glass  tubing  held 
lengthwise  in  the  blue  4  flame  of  a  burner  provided  with  a  wing 
top,  rotating  it  and  moving  it  from  left  to  right  until  it  softens, 
then  remove  it  from  the  flame  and  draw  it  out  very  slowly  at  first 
and  then,  as  the  glass  begins  to  cool  and  harden,  much  more 
rapidly,  into  a  long,  straight,  thin-walled,  narrow  tube  of  about 

flame,  and  when  it  melts  remove  it  from  the  flame  and  blow  a  bubble,  not  a  hole. 
Repeat  this  at  every  point.  Then  complete  the  making  of  the  holes  by  melting 
each  little  bubble  or  by  breaking  the  glass  with  a  file  and  "rounding"  the  edges 
of  each  hole  with  the  flame.  Remember  that  the  holes  should  be  not  more  than 
about  2  mm.  in  diameter. 

An  apparatus  like  the  one  described  above  but  without  the  holes  in  the  inner 
tube  has  been  in  use  for  many  years  in  different  laboratories.  It  is  believed,  how- 
ever, that  the  perforated  inner  tube  is  new  and  is  an  advantage  since  it  permits 
good  stirring  and  more  rapid  heating  and  cooling. 

1  If  a  long-scale  360°  thermometer  is  used,  this  cork  should  have  a  Ipngitudinal 
section  cut  out  to  form  a  canal  through  which  the  degrees  of  the  thermometer 
can  easily  be  read  at  this  interval. 

2  If  more  acid  is  used  the  melting-point  tube  is  likely  to  drop  off  in  the  liquid, 
since  too  small  a  length  of  it  is  held  by  capillary  attraction. 

3  The  currents  in  the  liquid  can  be  seen  very  nicely  if  a  little  finely  divided 
carbon  is  put  in  the  acid. 

4  A  smoky  flame  need  not  be  used  provided  the  tube  is  slowly  warmed  in  the 
blue  flame. 


LABORATORY  EXPERIMENTS  61 

i  mm.,  (it  0.2  mm.),  inside  diameter.1  Rapid  drawing  in  the  very 
beginning  makes  the  tube  too  narrow.  It  must  be  made  in  one 
heating.  The  wing-top  should  give  an  even  flame.  If  the  flame 
is  irregular  the  glass  will  not  be  heated  evenly  and  the  narrow 
tube  will  consequently  be  uneven.  Test-tubes  give  excellent 
melting-point  tubes.  They  are  heated  in  the  ordinary  Bunsen 
flame.  It  is  sometimes  difficult  to  make  a  tube  of  circular 
cross-section,  but  the  walls  are  sure  to  be  thin  and  this  is  an 
advantage  since  there  will  be  less  glass  through  which  the  heat 
must  be  conducted  to  the  substance.  Cut  the  long  narrow  tube 
into  lengths  of  9  cm.  by  means  of  file  marks  (do  not  try  to  break 
it  otherwise)  and  seal  one  end  of  each  tube  by  carefully  heating 
the  edges  in  the  outer  mantle  of  a  small  flame.  Do  not  fuse  too 
much  of  the  glass,  since  this  thickens  the  walls,  thus  diminish- 
ing the  diameter  of  the  tube,  and  causes  the  formation  of  a  glass 
bead  at  the  sealed  end.  Smaller  lengths  should  not  be  used  be- 
causs  they  will  not  remain  attached  to  the  thermometer  as  de- 
scribed below.  If  possible,  it  is  advisable  to  cut  the  original 
capillary  into  lengths  of  18  cm.  and  seal  both  ends.  When 
needed  the  double-length  tube  is  broken  at  the  center  and  serves 
for  two  determinations. 

Make  a  little  mound  of  dry,  powdered  2  substance  and  force 
some  of  this  into  a  melting-point  tube  by  gently  thrusting  the 
open  end  directly  into  the  material,  and  giving  it  a  rotary  motion 
at  the  same  time.  This  operation  cuts  out  a  little  cylindrical 
cake  of  the  substance.  Shake  this  down  by  letting  the  sealed 

1  Lengths  of  30  to  60  cm.  are  readily  made  in  this  way.    Larger  tubing  of  soft 
glass,  such  as  "bomb"  tubes,  can  be  drawn  out  rapidly,  with  the  aid  of  an  assist- 
ant, into  a  length  of  several  meters,  and  a  good  stock  of  melting-point  tubes  cut 
therefrom. 

The  advantages  of  the  long  straight  melting-point  tube  over  the  tapering  tube 
with  a  cup  at  the  top  which  has  often  been  described  are  threefold :  (i)  many  tubes 
can  be  made  at  the  same  time;  (2)  they  can  be  attached  more  easily  to  the  ther- 
mometer; and  (3)  most  organic  compounds  are  light  and  fluffy,  and  on  this  account 
they  cannot  be  made  to  drop  readily  to  the  bottom  of  the  melting-point  tube, 
but  since  the  straight  tube  has  an  even  bore,  the  little  cylinder  of  material  which 
is  cut  out,  as  described  in  the  next  paragraph  above,  will  usually  slide  down  to 
the  bottom  without  difficulty. 

2  Large  crystals  do  not  form  a  compact  mass  and  therefore  the  material  is  not 
heated  as  evenly  and  quickly  as  when  powder  is  used. 


62  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

end  of  the  tube  drop  gently  upon  the  desk.1  Repeat  until  a  layer 
3  mm.  deep  is  formed.  Rub  off  the  substance  adhering  to  the 
outside  of  the  tube  so  that  it  will  not  be  charred  by  the  acid  and 
discolor  the  bath.  Remove  the  thermometer  from  the  apparatus, 
allow  most  of  the  acid  to  drain  off,  and  touch  the  bulb  to  the 
upper  part  of  the  melting-point  tube,  thus  leaving  behind  a 
droplet  of  the  liquid.  Place  the  tube  with  the  sealed  end  down 
against  the  thermometer  stem  and  it  will  adhere  by  capillary 
attraction.  The  substance  should  be  opposite  the  bulb  of  the 
thermometer.  Return  the  thermometer,  with  the  tube  attached, 
to  the  apparatus.  The  melting-point  tube  should  extend  about 
as  far  along  the  thermometer  above  the  liquid  as  it  does  in  the 
liquid  in  order  that  the  capillary  force  will  be  great  enough  to 
hold  it  to  the  thermometer.  Now  begin  to  heat  the  liquid 
with  a  small  flame.2  The  heating  may  be  fairly  rapid  until 
within  about  15°  of  the  melting-point  (already  known  or  approxi- 
mately determined  in  a  preliminary  trial)  and  then  slowly, 
3°  a  minute,  until  the  substance  melts.  Do  not  guess  at  the 
rate,  time  it,  and  then  you  will  obtain  consistent  results.  Sub- 
stances generally  soften  and  contract,  and  often  become  dis- 
colored before  melting. 

It  is  absolutely  essential  to  use  a  small  flame,  and  heat 
regularly,  especially  when  within  io°-i5°  of  the  melting-point. 
Alternate  heating  with  a  large  flame  never  gives  consistent  results. 
The  small  flame  can  easily  be  obtained  if  the  air  supply  of  the 
burner  is  properly  cut  down.  Drafts  should  of  course  be  avoided 
as  much  as  possible. 

The  temperature  of  the  bath  can  be  carried  up  to  about 
280°  if  pure  cone,  sulfuric  acid  is  used.  If  water  has  been 
absorbed  the  diluted  acid  will  begin  to  boil  at  a  lower  tempera- 

1  If  the  substance  does  not  drop  readily  to  the  bottom  of  the  tube  try  either 
of  the  following  methods:   Hold  a  piece  of  ordinary  glass  tubing,  about  60  cm. 
long,  open  at  both  ends,  in  an  upright  position  on  the  desk  and  touching  the  desk 
top,  then  let  the  melting-point  tube,  with  sealed  end  down,  drop  through  it.    Repeat 
this  several  times  if  necessary.     Or,  draw  the  flat  side  of  a  triangular  file  hori- 
zontally across  the  tube  a  little  below  the  substance.    The  powder,  loosened  by 
the  vibration  set  up  in  the  glass,  will  quickly  slide  down  to  the  bottom. 

2  If  the  burner  is  held  in  the  hand,  hold  it  in  an  oblique  position  in  order  o  avoid 
accident  in  case  the  apparatus  cracks. 


LABORATORY  EXPERIMENTS  63 

ture  and  cannot  be  used  for  the  higher  temperatures.  If  it  begins 
to  boil  the  heating  should  be  discontinued.  The  boiling-point  of 
the  acid  may  be  increased  by  boiling  it  in  a  flask  or  beaker  under 
the  hood. 

The  errors  in  this  determination  are  generally  due  to  the  vari- 
ation of  the  thermometer,  rate  of  heating,1  physical  condition 
of  the  compound,2  and  individual  manipulation.  For  an 
extended  discussion  of  these  errors  the  student  is  referred  to  the 
bulletin  mentioned  in  the  foot-note  above.  The  true  melting- 
point  is  obtained  by  the  use  of  short-stem,  normal,  standardized 
thermometers  whose  mercury  thread  is  entirely  immersed  in 
the  bath.  Since  these  are  expensive  and  are  not  always  avail- 
able, the  set  of  three  short-scale  thermometers  mentioned  in 
connection  with  the  Boiling-point  experiment,  p.  8  and  Fig.  i, 
should  be  used. 

Experience  in  determining  the  melting-point  and  checks  on 
the  accuracy  of  the  thermometer  can  be  obtained  by  using 
substanc3s  whose  melting-points  are  near  the  bottom  and  some- 
what near  the  top  of  the  scale  in  each  case,  as  mentioned  in 
the  first  experiment.  The  following  substances  are  suitable. 
The  temperatures  given  are  corrected: 

Naphthalene 80.8° 

Benzoic  acid 122.5° 

Salicylic  acid 159.8° 

Anisic  acid 184 . 2  ° 

Anthracene 216.0° 

Carbazol 246 .  o° 

Anthraquinone 285 .  o° 

All  these  substances  in  addition  to  giving  good  melting- 
points  have  a  special  advantage  in  that  they  are  easily  obtained 

1  Probably  more  errors  are  made  in  manipulation  by  improper  heating  than  in 
any  other  way.    The  rate  of  heating  must  not  be  so  rapid  that  an  appreciable  rise 
of  temperature  occurs  during  the  time  necessary  for  the  attainment  of  the  same 
temperature  throughout  the  entire  mass.      Otherwise  the  temperature  may  rise 
several  degrees  during  the  interval  between  incipient  and  complete  melting. 

2  Compare  preceding  foot-note,  and  foot-note  2,  p.  61. 


64  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

and  are  readily  purified  by  sublimation.1  It  is  seldom  necessary 
to  use  a  substance  melting  below  naphthalene.  If  necessary 
one  of  the  following  can  be  used:  ^-toluidine,  45°;  hydrocin- 
namic  acid,  48.7°;  a-naphthylamine,  50°;  or  diphenylamine,  54°. 

Compare  the  results  with  those  obtained  with  the  same 
thermometers  in  the  boiling-point  experiment. 

If  the  set  of  three  thermometers  mentioned  above  is  not  at 
hand,  an  ordinary  long-scale  thermometer  may  be  standardized 
for  the  conditions  obtaining  in  the  laboratory  work  by  determin- 
ing the  melting-points  of  some  of  the  pure  substances  given  in 
the  list,  for  example,  naphthalene,  salicylic  acid,  anthracene  and 
carbazol.  Then  by  plotting  the  results  on  co-ordinate  paper,  as 
described  in  note  4,  Boiling-point  experiment,  p.  20,  the  cor- 
rection for  any  one  degree  may  quickly  be  read  off  at  any  time. 

The  influence  of  changes  in  atmospheric  pressure  on  the 
melting-point  is  negligible. 

The  abbreviation  "  cor."  is  placed  after  a  corrected  melting- 
point.  It  i's  to  be  noted  that  almost  all  the  melting-points  given 
in  the  literature  and  the  text-books  are  unfortunately  un- 
corrected.2  Melting-points  determined  under  uncorrected  con- 
ditions cannot  always  be  duplicated  by  other  workers.  This 
is  especially  true  of  melting-points  above  about  125°. 

NOTES 

i.  The  Thiele  melting-point  apparatus  is  shown  in  Fig.  10.  It 
uses  a  small  amount  of  acid  and  can  be  heated  and  cooled  quickly. 
The  flame  is  placed  under  the  bend  of  the  side  loop,  and  the  liquid 
is  stirred  by  means  of  convection  currents.  The  hot  current,  how- 
ever, usually  goes  down  the  side  near  the  loop,  and  the  remainder 
of  the  liquid  is  heated  mainly  by  conductance.  The  temperature 
of  the  sulfuric  acid  bath  can  be  carried  up  to  about  250°.  Then 
the  liquid  begins  to  boil,  and  bubbles  sometimes  form  rapidly  and 
exert  such  pressure  in  the  narrow  side  loop  that  the  tube  may  be 
cracked.  Very  good  results  can  be  obtained  with  this  apparatus 

1  For  a  simple  method  of  sublimation,  see  Anthraquinone,  Expt.  65,  p.  210. 

2  The  data  given  in  this  book  are  not  all  "corrected,"  since  they  cannot  always 
be  found  in  the  literature  and  very  pure  material  has  not  been  available. 


LABORATORY  EXPERIMENTS 


65 


when  the  heating  is  properly  carried  out.    It  is  quickly  affected  by 
drafts. 

2.  Discoloration  of  the  sulfuric  acid  on  account  of  charring  of 


C/amp 


Cork  with 
Canal 


Thiele  Melting -point 


FIG.  10. 


organic  matter  may  .be  prevented  to  a  limited  extent  by  the  addition 
of  very  small  amounts  of  potassium  nitrate,  sodium  persulfate, 
etc.,  or  the  discolored  acid  may  be  treated  with  cone,  nitric  acid  and 


66  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

boiled  in  a  flask  or  beaker  under  the  hood  until  the  fumes  of  nitric 
oxides  are  no  longer  evolved. 

3.  A  micro-burner  is  convenient  to  use  for  determinations  under 
100°. 

4.  Water  can  advantageously  be  used  for  determining  low  melt- 
ing-points. 

5.  A  skillful  operator  can  attach  several  different  melting-point 
tubes  to  the  same  thermometer  and  make  all  determinations  by  one 
continuous  heating  of  the  bath. 

6.  For  temperatures  between  220°  and  320°,  Mulliken1  recommends 
a  bath  prepared  by  cautiously  boiling  together  for  5  to  10  minutes, 
under  a  hood,  a  mixture  of  70  parts  by  weight  of  cone,  sulfuric  acid 
and  30  parts  of  neutral  potassium  sulfate,  and  stirring  until  the 
sulfate  is  completely  dissolved;  or  by  similar  treatment  of  a  mixture 
of  55  parts  by  weight  of  the  acid  with  45  parts  of  acid  potassium 
sulfate.    The  mixture  has  the  consistency  of  glycerol,  does  not  fume 
badly,  and  is  less  corrosive  and  less  easily  discolored  by  traces  of 
organic  matter  than  sulfuric  acid.    By  increasing  the  proportion  of 
neutral  sulfate  from  30  to  40  per  cent  this  bath  may  be  used  for 
temperatures  up  to  370°.    This  mixture,  however,  is  solid  at  the 
ordinary  temperature. 

For  temperatures  between  370°  and  500°,  fused  zinc  chloride, 
free  from  dust,  may  be  employed. 

The  student  is  referred  to  the  reference  cited  for  the  method  of 
handling  these  mixtures. 

7.  Certain  substances  which   decompose  at  high   temperatures 
giving  off  water  vapor,  carbon  dioxide,  or  ammonia,  give  better  melting- 
points  when  heated  in  melting-point  tubes  sealed  at  both  ends. 
Complete  data  as  to  size  of  tube,  quantity  used,  etc.,  are  necessary 
for  comparison,  because  they  will  vary  many  degrees  with  a  change 
in  conditions  on  account  of  the  differences  in  the  gas  pressures  of 
the  decomposition  products. 

Similarly  substances  which  readily  sublime  are  sometimes  heated 
in  melting-point  tubes  sealed  at  both  ends. 

8.  It  is  not  always  possible  to  determine  the  melting-point  a 
second  time  on  the  same  sample  previously  melted  in  the  tube,  since 
in  many  cases  the  substance  decomposes.    It  should  also  be  mentioned 
that  in  some  cases  the  substance  undergoes  a  change  in  its  crystalline 
condition,  being  converted  from  an  unstable  form  into  the  stable 

1  "Identification  of  Pure  Organic  Compounds,"  Vol.  I,  218-9. 


LABORATORY  EXPERIMENTS  67 

form,1  like  iodine  monochloride,  and  phosphorus.  For  example, 
the  labile  or  metastabile  form  of  benzophenone  melts  at  26°,  but 
after  having  been  melted  and  allowed  to  solidify,  if  heated  again, 
it  is  found  to  melt  at  48°.  Sometimes  the  difference  is  much  greater 
than  in  this  example,  sometimes  it  is  very  much  less.  The  changes 
from  one  form  to  the  other  may  be  very  rapid  or  very  slow.  If  the 
melting-point  is  taken  very  slowly  the  metastabile  form  may  be 
transformed  into  the  stable  form  and  only  the  melting-point  of  the 
stable  form  actually  noticed. 

In  other  cases  the  stable  form  may  have  the  lower  melting-point. 
The  stable  form  of  benzaldoxime  melts  at  34-5°  and  the  unstable 
at  130°.  These  two  forms,  however,  are  isomeric,2  not  polymorphic 
like  benzophenone,  and  the  change  is  supposed  to  be  stereoisomeric. 

Furthermore  there  are  a  few  known  cases  where  the  substance 
melts  sharply  at  a  definite  temperature  to  a  milky  liquid,  which 
on  being  further  heated  suddenly  becomes  clear  also  at  a  definite 
temperature.  On  cooling  the  reverse  series  of  changes  occurs.  Since 
these  milky  or  turbid  liquids  show  properties  of  both  liquids  and 
solids  they  have  been  called  liquid  crystals?  The  crystalline  structure 
of  the  turbid  liquid  cannot  be  detected  by  the  microscope,  but  is 
indicated  by  the  double  refraction  exhibited  by  the  liquid,  and  by 
the  formation  of  the  figures  characteristic  of  double-refracting  crys- 
tals between  crossed  Nicol  prisms  in  converging  light. 

1  Such  a  substance  is  called  monotropic.    For  a  discussion  of  this  phenomenon, 
see  Findlay,  "The  Phase  Rule,"  4th  Ed.  (1914),  46-9;  and  Holleman,  "Organic 
Chemistry,"  4th  Ed.   (1914),  430;    and  Lehmann,   "Molecularphysik"   (1888), 
Vol.  I,  193-213,  291-309,  687-695.    The  following  common  substances  exist  in 
these    two  modifications:    benzophenone,  ^-tolyl-phenyl-ketone,  /3/3-dibrom-pro- 
pionic  acid,  mono-chloracetic  acid,  acetanilide,  a-triphenyl-guanidine,  w-chlor- 
nitrobenzene,  ^-nitrophenol,  diphenyl-naphthyl-methane,triphenylmethane,  penta- 
methyl-leucaniline,  styphnic   acid,  w-dinitro-benzene,  resorcinol,  hydroquinone, 
trinitro-w-cresol,  phthalic  acid,  stilbene-dichloride,  benzoin,  mandelic  acid,  cin- 
namic  acid,  carbostyril,  mercury-diphenyl,  limonene-tetrabromide,  etc. 

2  See  Findlay,  "The  Phase  Rule,"  4th  Ed.  (1914),  208-11;  Holleman,  "Organic 
Chemistry,"  4th  Ed.  (1914),  431-3;  and  Sidgwick,  "The  Organic  Chemistry  of 
Nitrogen,"  (1910),  118. 

3 For  discussion  see  Findlay,  'The  Phase  Rule,"  4th  Ed.  (1914),  55-8;  and 
Holleman,  "Organic  Chemistry,"  4th  Ed.  (1914),  408.  Cholesteryl  benzoate 
melts  to  a  milky  liquid  at  145.5°  and  to  a  clear  liquid  at  178.5°.  Azoxyanisole, 
azoxyphenetole,  and  />-methoxy-cinnamic  acid  also  show  a  similar  behavior. 


68  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 


QUESTIONS 

i    Discuss  some  of  the  errors  in  the  ordinary  method  of  deter- 
mining the  melting-point. 

2.  Why  is  it  necessary  to  heat  slowly  when  the  temperature  is 

near  the  melting-point? 

3.  Why  should  the  substance  be  powdered? 

4.  What  objection  is  there  to  the  use  of  a  rubber  band  for  holding 

the  melting-point  tube  to  the  thermometer? 

5.  What  advantage  does  cone,  sulfuric  acid  have  over  glycerine 

and  cottonseed  oil  as  used  in  the  melting-point  apparatus? 
(Compare  behavior  on  heating.) 

6.  What  bath  is  used  for  taking  melting-points  above  300°? 

7.  What  is  the  object  of  adding  sometimes  a  crystal  of  potassium 

nitrate  or  sodium  persulfate  to  the  cone,  sulfuric  acid  bath? 

8.  Given  two  substances  having  the  same  melting-point,  if  one 

is  known,  how  can  you  tell  whether  the  other  compound 
is  identical  with  the  first  by  means  of  the  melting-point  ! 
determination?     Explain. 

9.  What  advantage  has  water  over  cone,  sulfuric  acid  for  deter- 

mining low  melting-points?     (Compare  specific  heats.) 


Experiment  No.  13 

FORMATION  OF  A  TERTIARY  ALCOHOL  BY  MEANS  OF  GRIGNARD'S 

REACTION 


Preparation  of  Dimethyl-ethyl-carbinol    (2-methyl-butanol-2) 


The  success  of  this  experiment  depends  on  the  absence  of 
water  until  after  the  ketone  is  all  added.     Therefore  the  appara- 
tus and  substances  used  must  be  perfectly  dry.     Dry  the  acetone 
with  anhydrous  potassium  carbonate  or  anhydrous  sodium  sul- 
:  fate,  the  ethyl  bromide  with  calcium  chloride,  and  the  "  absolute  " 
ether  with  very  thin  slices  of  clean  sodium  in  a  flask  provided  with 
a  calcium  chloride  tube.2    Let  them  all  stand  at  least  overnight. 
i  Use  larger  amounts  than  called  for  below  since  some  is  absorbed 
|  by  the  drying  agents.     The  "  ether  over  sodium  "  or  "  absolute  " 
I  ether  as  obtained  from  the  stockroom  must  be  dried  again  because 
'  it  cannot  be  kept  free  from  water  in  the  ordinary  containers. 
The  ordinary  ether  can  be  used  for  this  experiment  if  it  is  treated 
as  follows:     Shake  it  two  or  three  times  with  different  portions 
of  a  saturated  solution  of  salt  in  order  to  remove  the  alcohol  and 
dry  first  with  calcium  chloride  and  then  with  sodium.3    If  it  is 
turbid  at  the  end  of  the  drying,  it  should  be  distilled  under  an- 
hydrous conditions   (see  Absolute  Alcohol,  p.    26),  and  then 
dried  again  with  sodium  before  use  in  the  experiment. 

1The  Geneva  or  official  nomenclature  is  outlined  in  Amer.  Chem.  Journ.,  15 
(1893),  50. 

2  During  warm  weather  a  small  reflux  condenser  in  addition  should  be  used  to 
prevent  excessive  evaporation  of  the  ether. 

3  Sodium  residues:    Great  care  should  be  exercised  in  handling  the  residue  of 
sodium.    It  should  not  be  put  into  the  sink  or  the  waste  jar,  but  should  always  be 
destroyed  by  adding  it  in  small  pieces  to  some  alcohol  or  acetone  in  a  beaker, 
waiting  until  practically  all  action  has  ceased  with  each  piece  before  adding  another. 
Then  (Care!)  pour  the  solution  into  the  sink,  a  little  at  a  time.    Also  rinse  the 
flask  with  alcohol  or  acetone  before  adding  any  water. 

69 


70  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

Ether  Distillation. — Ether  must  be  kept  away  from  flames. 
Its  vapor  is  heavier  than  air  and  very  inflammable,  and  therefore 
the  heating  for  the  distillation  must  be  done  with  steam  or 
warm  water.  In  ether  distillation  use  an  Erlenmeyer  suction  flask 
as  a  receiver  connected  as  in  the  Absolute  Alcohol  experiment, 
p.  27,  but  with  a  long  rubber  tube  attached  to  its  outlet  tube  and 
leading  below  the  level  of  the  desk  to  carry  away  the  fumes. 
When  small  quantities  are  distilled  an  ordinary  flask  may  be  used 
as  a  receiver  and  the  space  between  the  condenser  tube  and  mouth 
of  the  flask  loosely  plugged  with  cotton  to  prevent  the  circulation 
of  the  vapors. 

Have  all  necessary  connections  ready  before  the  experiment 
is  started. 

To  a  250  cc.  flask  containing  5  grams  of  dry  magnesium 
turnings  attach  an  addition  tube  and  reflux  condenser  with  inner 
tube  dry.1  Insert  a  dropping-funnel 2  in  the  addition  tube  and 
connect  a  calcium  chloride  tube  filled  half  with  calcium  chloride 
and  half  with  soda  lime  (to  remove  carbon  dioxide) .  The  soda 
lime  should  be  next  to  the  large  open  end  of  the  tube.  Add  25  • 
cc.  of  dry  ether  to  the  flask.  Place  a  solution  of  30  cc.  (44  grams) 
of  dry  ethyl  bromide  (twice  the  theoretical  amount  required  ac- 
cording to  the  equation)  in  15  cc.  of  dry  ether  into  the  bulb 
of  the  funnel,  stopper  loosely  and  let  this  slowly  drop  into  the 
flask.  A  vigorous  reaction  begins  after  the  first  small  portion  has 
been  added.  Moderate  by  surrounding  the  flask  with  cold  water. 
If  it  does  not  start  spontaneously,  warm  the  flask  with  the  hand 
or  add  a  crystal  of  iodine.  Shake  frequently.  After  the  reac- 
tion is  well  started  add  50  cc.  of  the  dry  ether  direct  to  the 
mixture  by  pouring  it  through  the  condenser.  When  practically 
all  the  magnesium  has  disappeared  cautiously  add,  with  shaking 
and  good  cooling,  a  solution  of  15  cc.  (12  grams)  of  dry  acetone 
and  10  cc.  of  dry  ether  from  the  dropping-funnel.  Each  drop 
reacts  with  a  hiss  and  causes  a  white  precipitate  which  at  first 
redissolves  but  later  settles  down  as  a  bluish-gray,  viscous  mass. 

1  See  Fig.  3,  p.  13. 

2  The  connection  can  sometimes  be  made  with  a  piece  of  rubber  tubing  instead 
of  a  cork. 


LABORATORY  EXPERIMENTS  71 

After  the  reaction  is  complete  cautiously  decompose  the 
addition  product  by  adding,  from  the  funnel  during  about 
thirty  minutes,  the  calculated  amount  of  sulfuric  acid  1  in  140  cc. 
of  water.  During  this  treatment  place  the  flask  in  ice  and  shake 
frequently.  A  flocculent  white  precipitate  is  formed  at  first 
but  is  later  dissolved.  (?)  Separate  the  ethereal  solution  which 
contains  the  product,  and  dry  with  fused  potassium  carbonate. 
Remove  the  ether  by  distillation,  observing  the  precautions 
mentioned  above,  and  fractionate  the  residue  in  a  small  distilling 
flask.  Since  the  carbinol  is  volatile  with  ether  collect  the 
distillate  in  the  following  fractions:  7o°-95°,  95°-io5°,  105°- 
110°,  then  redistill  each,  collecting  the  portion  distilling  ioo°- 
104°  as  the  sample.  Pure  dimethyl-ethyl-carbinol  boils  at  102° 
and  has  a  specific  gravity  of  0.8069  at  25°-  Yield,  40  per  cent 
of  the  theory. 

Test  the  first  runnings  of  the  distillate  for  unsaturated  com- 
pounds with  bromine  in  carbon  tetrachloride,  and  with  dilute 
potassium  permanganate.  (?) 

NOTE 

Magnesium  turnings  for  use  in  the  Grignard  reaction  must  be 
prepared  fresh  or  kept  in  a  bottle  whose  cork  has  been  covered  with 
melted  paraffin  to  prevent  the  entrance  of  moisture.  Otherwise 
the  magnesium  becomes  coated  with  the  hydroxide,  etc.,  and  does 
not  react  well. 

REFERENCES 

Gattermann,  "Practical  Methods  of  Organic  Chemistry,"  3d 
Amer.  Ed.,  350-4;  Wren,  "The  Organometallic  Compounds  of  Zinc 
and  Magnesium"  (Van  Nostrand,  1913),  1-26,  72-9;  Nelson  ana 
Evans,  "Electromotive  force  developed  in  cells  containing  non- 
queous  liquids,"  Journ.  Amer.  Chem.  Soc.,  39  (1917),  82. 

QUESTIONS 

1.  How  does  moisture  cause  trouble  in  this  experiment? 

2.  Why  is   absence   of  water  unimportant  after  the  ketone 

has  been  added? 

1Conc.  sulphuric  acid  of  sp.  gr.  1.84  contains  approximately  96%  H2SO4 
by  weight.  Make  sure  of  your  equation  before  making  this  calculation. 


72  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

3.  Why  isn't   ordinary   ether   used   and   dried   directly  with 

calcium  chloride  as  in  the  case  of  the  acetone? 

4.  Why  cannot  the  acetone  be  dried  with  metallic  sodium? 

5.  What  other  solvent  besides  ether  can  be  used  for  this  experi- 

ment?   Why? 

6.  What  reactions  take  place  when  ether,  magnesium,   and 

ethyl  bromide  are  brought  together? 

7.  Why  is  the  flask  containing  this  reaction  mixture  kept  in 

cold  water? 

8.  Why  is  the  acetone  added  cautiously? 

9.  Can  the  acetone  be  added  directly  with  the  ethyl  bromide 

to  the  ether  and  magnesium  mixture?  (Compare  Davies 
and  Kipping,  Jour.  Chem.  Soc.,  99  (1911),  296-301.) 

10.  What  would  happen  if  carbon  dioxide  came  in  contact 
with  the  Grignard  reagent? 

n.  Is  the  magnesium  oxidized  or  reduced  in  the  experiment? 

12.  What  would  be  formed  if  only  water  was  added  at  the  end  of 

the  reaction? 

13.  What  is   the  purpose   of   adding   acid?     Is   it  absolutely 

necessary? 

14.  Could  cone.  EbSCU  be  used  in  place  of  dilute  acid? 

15.  What  causes  the  bubbling  that  often  occurs  after  all  the 

dilute  acid  has  been  added? 

16.  What  might  be  some  of  the  impurities  in  the  crude  tertiary 

alcohol?  (Compare  the  properties  of  the  "first  umnings" 
of  the  distillate.) 

17.  Explain  what  is  meant  by  the  term  "  volatile  with  ether." 

(Compare  fractionation  of  liquids  which  mix  in  all  pro 
portions.) 

1 8.  Why  use  a  small  distilling  flask  in  the   redistillation   o 

dimethyl-ethyl-carbinol? 

19.  How  does  this  pentyl  (amyl)  alcohol  differ  from  the  isomy 

alcohol  of  commerce? 

20.  The  amount  of  ethyl  bromide  (30  cc.)  is  twice  the  amoun 

required  by  the  theoretical  equation.     Why  is  it  necessa 
to  use  an  excess? 


Experiment  No.  14 

REDUCTION  OF  A  KETONE  TO  A  SECONDARY  ALCOHOL  (SODIUM 
ALCOHOL  REDUCTION) 

Preparation  of  Methyl-phenyl-carbinol  from  Acetophenone 
(M  ethyl-phenyl-ketone) 

Dissolve  10  grams  (10  cc.)  of  acetophenone  in  125  cc.  of  al- 
cohol in  a  5OO-CC.  flask,  with  an  addition  tube  attached  and  a 
reflux  condenser  connected  with  the  side  tube..  Prepare  10 
grams  of  clean  metallic  sodium  1  cut  in  strips  narrow  enough 
to  slip  through  the  vertical  tube  easily.  Add  these  strips  to  the 
alcoholic  olution  through  the  vertical  tube  a  few  at  a  time  and 
let  the  reaction  abate  somewhat  before  the  addition  of  others. 
The  reduction  should  be  strong  and  the  alcoholic  solution  should 
boil  vigorously,  but  at  the  same  time  the  reaction  must  be  kept 
in  hand. 

When  all  the  sodium  has  dissolved,  distill  off  as  much  as  pos- 
sible of  the  alcohol,  in  vacuo.  Since  it  is  difficult  to  transfer  the 
reaction-mixture,  which  is  very  viscous,  and  since  there  is  a  great 
deal  of  foaming  during  the  distillation,  the  original  flask  is  used 
for  this  first  distil  ation  instead  of  the  Claisen  flask  described  in 
the  accompanying  d  rections  or  vacuum  d'stillation,  Expt.  15, 
p.  76.  Slant  the  flask  in  order  to  allow  the  foam  to  "  break  " 
against  the  walls  and  not  pass  out  into  the  distillate.  Connect 
it  with  a  bent  tube  leading  into  a  distilling-flask  which  acts  as  a 
receiver  (Compare  Fig.  n).  The  receiver  need  not  be  cooled 
in  this  case;  let  the  alcohol  vapors  pass  through  uncondensed. 
The  receiver  is  used  to  catch  any  of  the  product  which  some- 
times distills  or  goes  over  with  some  foam.  Heat  the  main  flask 

1  Use  a  common  knife  or  pen-knife  to  cut  the  sodium  and  dip  the  blade 
frequently  into  the  kerosene  with  which  the  sodium  is  covered  Return  all  resi- 
dues to  the  original  bottle  or  destroy  them  with  alcohol,  as  mentioned  under 
Dimethyl-ethyl-carbinol,  p.  69. 

73 


74  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

with  water  kept  at  5o°-6o°,  and  frequently  shake  the  flask 
somewhat  to  change  the  surface  of  the  mixture  and  thus  permit 
rapid  vaporization.  The  distillation  requires  from  one  to  two 
hours.  As  it  progresses  the  mixture  becomes  a  darker  brown, 
and  pasty. 

When  practically  all  the  alcohol  is  distilled  over  add  50  cc. 
of  water  and  then  exactly  neutralize  the  solution  with  acetic 
acid.  Distill  off  the  remaining  alcohol  in  vacuo  from  the  same 
flask  and  in  the  same  manner  as  before. 

Ether  Extraction.  Transfer  the  residue  to  a  separatory 
funnel  with  the  aid  of  water  and  a  little  ether,  and  extract  it  with 
ether  as  follows:  Add  about  30  cc.  of  ether  (and  if  necessary 
enough  water  to  dissolve  any  precipitate),  stopper  securely, 
invert  the  funnel,  holding  the  stopper  in  with  one  hand  and  plac- 
ing the  thumb  of  the  other  hand  on  the  handle  of  the  stop-cock 
and  the  first  two  fingers  on  the  other  side  of  the  stem  and  shake. 
While  it  is  still  inverted  open  the  stop-cock  to  release  the  pres- 
sure 1  within  the  funnel.  Cloze  the  stop-cock  and  shake  again, 
frequently  releasing  the  pressure.  Turn  the  funnel  right  side 
up,  support  it  in  a  ring,  allow  to  settle,  draw  off  the  aqueous 
layer  into  a  beaker,  and  pour  the  ethereal  solution  from  the  top 
of  the  funnel  into  a  dry  Erlenmeyer  flask.  Return  the  aqueous 
layer  to  the  funnel,  repeat  the  extraction  with  about  the  same 
amount  of  ether,  and  add  the  ethereal  solution  to  the  first  por- 
tion in  the  Erlenmeyer  flask. 

If  some  of  the  product  was  distilled  over  into  the  receivi 
flask,  the  material  thus  collected  should  be  extracted  with  ether 
provided  it  contains  practical" y  no  alcohol,  and  added  to  th 
main  ethereal  solution.     If  it  contains  much  alcohol  it  cannot 
very  well  be  extracted  with  ether  (?),  and  the  alcohol  must  be 
evaporated  off  before  extraction. 

If  the  main  ether  extract  is  acid  to  litmus,  neutralize  it  by 
shaking  with  a  solution  of  sodium  carbonate. 

Dry  the  ethereal  solut  on  with  fused  potassium  carbonate, 
transfer  it  to  a  Claisen  distilling-flask,  remove  the  ether  by 

1  In  this  laboratory  there  arc  two  cases  on  record  where  the  separatory  funnel 
exploded  on  account  of  carelessness  in  disregarding  this  procedure. 


LABORATORY  EXPERIMENTS  75 

distillation  under  the  usual  conditions  and  then  distill  the  residue 
in  vacuo,  in  accordance  with  the  directions  given  in  Expt.  15, 
following  this.  Some  ether  will  pass  over  first,  the  temperature 
then  rises  and  the  carbinol  distills.  It  boils  at  118°  at  40  mm., 
106°  at  21  mm.,  and  98°  at  15  mm.  At  atmospheric  pressure, 
it  boils  with  partia  decomposition  at  about  202°.  The  yield 
is  about  40  per  cent  of  the  theoretical  amount. 

REFERENCES  FOR  ETHER  EXTRACTION 

Walker,  "Introduction  to  Physical  Chemistry,"  ;th  Ed.  (1913), 
59-61;  Alex.  Smith,  "Introduction  to  Inorganic  Chemistry,"  3d 
Ed.  (1917),  189. 

QUESTIONS 

1.  Why  is  alcohol  used  in  this  experiment? 

2.  Is  all  the  alcohol  used  up  during  the  reaction? 

3.  What  becomes  of  the  sodium  ethoxide? 

4.  Point  out  what  is  reduced  and  what  is  oxidized. 

5.  Is    the    methyl-phenyl-carbinol    formed    acted     upon    by 

sodium? 

6.  What  other  organic  compound  is  likely  to  be  formed? 

7.  Is  this  a  "  higher  "  or  "  lower  "  reduction  product  of  the 

ketone? 

8.  Why  is  sodium  used  instead  of  some  other  metal  like  zinc? 

9.  Why  does  sodium  react  with  alcohol  while  zinc  does  not? 

10.  Where  does  the  "  remaining  alcohol  "  come  from? 

11.  How  could  you  calculate  how  much  of  this  "remaining 

alcohol  "  there  would  be? 

12.  Why  is  it  necessary  to  distill  off  this  alcohol  before  extracting 

with  ether? 

13.  Why  is  the  ethereal  solution  poured  from  the  top  of  the  sep- 

aratory  funnel? 

14.  Discuss  the  extraction  of  aqueous  solutions  and  mixtures 

of  organic  substances  with  immiscible    liquids,  such  as 
ether,  chloroform,  benzene,  etc. 

15.  What  is  meant  by  the  Coefficient  of  Partition  or  Distribu- 

tion?    (See  references   above.) 

1 6.  Why  is  it  .necessary  to  distill  in  a  vacuum? 

17.  What  is  the  boiling-point  of  acetophenone? 

1 8.  How  could  the  presence  of  any  unchanged  acetophenone 

be  shown  in  the  product? 

19.  Is  the  methyl-phenyl-carbinol  as  prepared  in  the  laboratory 

optically  active?    Explain. 


Experiment  No.  15 
Distillation  in  vacua  or  under  Diminished  Pressure 

Distillation  in  vacuo  or  under  diminished  pressure  is  always 
resorted  to  if  the  compound  decomposes  when  heated  at  atmos- 
pheric pressure,  but  is  volatile  without  decomposition  at  lower 
pressures.  The  apparatus  employed  is  indicated  diagrammatic- 
ally  in  Fig.  ii.  A  Claisen  distilling-flask  is  used  since  it  has  a 
side  arm  which  helps  to  prevent  any  liquid  from  being  sprayed 
up  into  the  outlet  tube  if  the  liquid  should  bump  violently,  and 
since  tighter  joints  can  be  obtained  by  connecting  the  ther- 
mometer and  the  capillary  extension  tube  with  heavy  rubber 
tubing  outside  than  when  rubber  stoppers  are  used.  Attach 
an  ordinary  distilling-flask  as  the  receiver  with  a  rubber  stopper, 
making  certain  that  the  outlet  tube  of  the  Claisen  flask  projects 
into  the  bulb  of  the  receiver  in  order  that  the  vapors  of  the  dis- 
tillate may  not  be  carried  off  by  the  suction.  During  the  dis- 
tillation cool  it  with  running  water.1  Support  both  flasks  with 
clamps.  If  the  temperature  of  the  distillate  under  the  diminished 
pressure  exceeds  160°  the  rubber  stopper  in  the  receiver  should 
be  changed  for  a  good  cork  stopper.  Rubber  stoppers  soften  and 
gradually  melt  above  this  temperature.  A  good  cork  stopper 
can  sometimes  be  made  air-tight  by  coating  it  with  collodion 
after  the  apparatus  has  been  fitted  up.  Connect  the  delivery 
tube  of  the  receiver  by  means  of  rubber  "  pressure  "  tubing  to  a 
manometer  and  a  water  pump.  By  using  glass  tubing  and  short 
rubber  connections  only  a  small  amount  of  the  expensive  "  pres- 
sure "  tubing  is  necessary.  All  glass  connecting  tubing  should 
have  smooth,  rounded  ends. 

1  The  cooling  is  made  more  efficient  if  a  piece  of  cloth  is  wrapped  around  tl 
bulb  of  the  receiving  flask. 

76 


LABORATORY  EXPERIMENTS 


77 


78  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

A  good  water  pump  will  give  a  pressure  in  the  apparatus 
as  low  as  the  vapor  tension  of  the  water  at  its  particular  tem- 
perature. In  winter  when  the  temperature  of  the  water  may  be 
8°,  at  which  the  vapor  tension  of  the  water  is  7.99  mm.,  the 
pressure  within  the  apparatus  may  approach  8  mm.,  but  in  sum- 
mer when  the  temperature  of  the  water  may  be  as  high  as  23° 
a  pressure  cannot  be  obtained  lower  than  21  mm.,  which  is  the 
vapor  tension  of  the  water  at  that  temperature.1 

The  general  connections  for  vacuum  distillation  are  made 
as  follows:  Outlet  tube  of  the  receiver  to  an  Erlenmeyer  suc- 
tion flask  and  the  latter  to  the  water  pump  and  the  manometer. 
The  tube  connecting  the  suction  flask  with  the  pump  should 
extend  to  the  bottom  of  the  flask  in  order  that  any  water  which 
may  come  over  on  account  of  unequal  pressure  in  the  water 
main  will  be  sucked  right  out  as  soon  as  the  greater  water  pres- 
sure returns.  A  three-holed  rubber  stopper  is  used  in  the  mouth 
of  the  suction  flask.  This  provides  for  the  tube  to  the  pump, 
just  mentioned,  for  the  tube  connecting  the  manometer,  and  for 
a  glass  stop-cock  which  is  used  for  equalizing  the  pressure  when 
necessary  (or  this  glass  stop-cock  may  be  placed  between  the 
receiver  and  the  suction  flask).  A  "  vacuum  "  valve2  may  be 
placed  just  before  the  pump.  Instead  of  using  a  distilling- 
flask  as  the  receiver  it  is  often  convenient  for  small  amounts 
of  high-boiling  liquids  or  solids  to  use  a  "  suction  "  test-tube— 
a  test-tube  with  a  side  outlet  tube.  In  some  cases,  a  sample 
tube  can  be  placed  inside,  and  then.it  will  not  be  necessary  to 
transfer  the  distillate. 

In  order  to  prevent  bumping  the  vapor  phase  is  introduced 

1  For  pressures  lower  than  these,  a  good  oil  pump  must  be  used.    Then  it  is 
possible  to  go  down  to  o.i  mm. 

A  table  of  the  vapor  pressure  (tension)  of  water  at  different  temperatures  is 
given  on  p.  301. 

2  Not  shown  in  the  figure.    A  "vacuum"  valve  consists  of  a  glass  tube  bent 
in  the  form  of  a  narrow  inverted  U  with  elongations  at  the  end;  for  connecting 
purposes.    One  arm  contains  a  free-moving  hollow  glass  plunger  which  is  ground 
at  one  end  to  fit  into  a  corresponding  ground  glass  seat  formed  by  a  constriction. 
When  the  pressure  suddenly  changes  the  plunger  moves  up  into  the  ground  seat 
and  closes  the  tube  automatically,  and  moves  out  again  when  the  pressure  is 
reversed.    It  serves  to  keep  waier  from  being  drawn  into  the  apparatus. 


LABORATORY  EXPERIMENTS  79 

by  using  pieces  of  porous  tiling l  in  the  liquid,  or  better  by 
passing  a  rapid  continuous  stream  of  tiny  air  bubbles  through 
the  liquid  (see  discussion  in  note  2,  p.  18,  of  the  Boiling-point 
experiment).  An  ordinary  glass  tube  is  drawn  out  into  a  fine 
capillary,  and  cut  off  at  the  proper  length.  To  the  wide  end  is 
attached  a  short  piece  of  rubber  tubing  with  a  screw  clamp  at 
its  upper  end  to  regulate  the  bubbling.2  Sometimes  the  capillary 
can  be  made  so  fine  that  no  other  regulation  will  be  necessary. 
A  slight  drawback  to  this  method  is  that  it  introduces  an  error 
in  the  boiling-point,  as  the  pressure  registered  when  air  is 
present  will  be  the  sum  of  the  partial  pressures  of  the  vapor 
and  of  the  air. 

The  distilling-flask  should  not  be  more  than  one-third  full.  It 
is  heated  by  means  of  a  water  or  an  oil-bath,3  according  to  the 
temperature  required.  Good  results  are  obtained  by  immersing 
the  bulb  of  the  flask  at  least  two-thirds  into  the  bath.  The  vapor 
is  not  superheated  so  much  as  under  ordinary  conditions  on 
account  of  the  rarefaction  of  the  vapor  and  less  heat  conduct- 
ance. A  thermometer  is  kept  in  the  oil  and  the  temperature 
of  the  oil  should  not  ordinarily  be  more  than  2o°-3o°  higher 
than  the  temperature  at  which  the  liquid  in  the  flask  distills. 
The  heating  is  not  begun  until  the  apparatus  is  exhausted. 
Sometimes  it  is  necessary  to  prevent  radiation  by  wrapping 
filter  or  asbestos  paper  around  the  neck  of  the  flask  below  the 
outlet  tube. 

1  The  porous  tiling  loses  its  efficiency  within  a  short  time,  probably  because 
the  air  is  given  up  more  rapidly  under  the  reduced  pressure. 

2  If  an  ordinary  distilling-flask  is  used  instead  of  the  Claisen  distilling-flask, 
and  if  there  is  not  space  enough  for  both  thermometer  and  the  glass  bubbling 
tube  in  the  neck,  the  thermometer  may  be  placed  within  the  tube  and  a  one-holed 
stopper  used. 

3  Rape-seed  oil  is  good  to  use.     Paraffin  or  paraffin  oil  smokes  a  great  deal. 
The  rape-seed  oil  also  smokes  somewhat  at  first  and  gives  off  a  pungent  odor, 
but  after  two  or  three  heatings  it  does  not  smoke  so  much.    It  can  be  carried  up 
to  about  300°.    A  metal  bath  has  the  advantage  that  it  does  not  smoke  and  is  not 
liable  to  catch  fire,  but  it  is  solid  at  ordinary  temperatures.    Following  are  alloys 
which  can  be  used  for  low-melting  baths:    Wood's  metal,  1-2  parts  of  cadmium, 
2  of  tin,  and  7-8  of  bismuth,  melts  at  71°;  Rose's  metal,  2  parts  of  bismuth,  i  of 
lead,  and  i  of  tin,  melts  at  95°;  an  alloy  of  i  part  of  lead  and  2  of  bismuth,  melts 
at  120°.    If  the  flask  which  is  heated  in  such  metal  baths  is  coated  with  graphite 
the  metal  will  not  stick  to  the  glass. 


L-iV 

; 

be 


80  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

It  is  best  to  test  the  apparatus  before  putting  in  the  substance 
in  order  to  determine  whether  the  glass  is  perfect  and  the  joints 
are  tight.  In  this  way  a  loss  of  material  may  often  be  avoided. 

^Vhen  carrying  out  a  vacuum  distillation  it  is  advisable  to 
protect  the  eyes  with  goggles,  or  use  a  glass  screen. 

At  the  end  of  the  distillation  the  stop-cock  should  be  grad- 
ually opened  before  the  water  is  turned  off.  If  the  stop-cock 
is  used  between  the  receiver  and  the  suction  flask,  the  stopper 
itself  is  gradually  and  carefully  removed.  This  allows  the  ine~- 
cury  column  to  settle  slowly  and  also  prevents  water  vapor  fro 
being  sucked  into  the  apparatus. 

The  Manometer.  The  manometer  consists  of  a  glass  tube 
bent  in  such  a  way  as  to  hold  a  column  of  mercury,  a  scale, 
and  a  stand  for  a  support,  as  shown  in  the  figure.  The  short 
length  of  the  glass  tube  should  be  about  50  cm.  long  and  the 
longer  length  85  cm.  The  lower  bend  can  be  made  by  one 
heating  in  a  smoky  flame.  After  the  mercury  has  been  poured 
in,1  insert  a  plug  of  cotton  to  keep  out  foreign  matter  and  place 
a  small  test-tube  over  it.  By  slanting  the  manometer  when  the 
mercury  is  added  any  air  bubbles  will  come  out  readily,  especially 
if  the  tube  is  tapped.  The  glass  tube  should  be  dry  and  free  from 
dust,  grease,  etc.  If  the  mercury  does  not  run  free  from  bubbles 
wash  the  tube  with  alcohol  and  ether  and  remove  the  adhering 
ether  with  a  current  of  air.  The  column  of  mercury  is  of  such  a 
height  that  when  the  apparatus  is  exhausted  the  lower  and  upper 
limits  of  the  mercury  will  be  opposite  some  point  on  the  scales 
described  below.  The  glass  tube  is  connected  with  the  suction 
flask. 

To  Make  the  Scale.  Select  any  point,  X,  not  less  than 
38  cm.  above  the  lowest  bend  in  the  glass  tubing,  and  attach 
narrow  strips  of  paper  (Y  and  Z)  near  the  top  and  the  bottom  of 
the  stand  in  the  positions  shown.  Measuring  from  the  point  X 
mark  on  the  papers  numbers  showing  28  to  38  cm.  up  and  down 
respectively.  Ruled  centimeter  paper  is  very  convenient,  and 
when  this  is  used  it  should  not  be  attached  until  a  definite 
point  opposite  a  centimeter  line  has  been  located. 

1  Use  a  small  funnel  connected  by  means  of  rubber  tubing  to  the  manometer  tube. 


LABORATORY  EXPERIMENTS  81 

Instead  of  these  scales  a  meter  stick  can  be  fastened  to  the 
stand  and  the  different  heights  read  directly. 

To  Calculate  the  Pressure  within  the  Apparatus.  Add  the 
figures  on  the  lower  and  upper  scales  opposite  the  top  of  the 
mercury  meniscus  x  in  each  case  and  subtract  the  sum  of  these 
numbers  from  the  barometric  reading.  Record  both  the  boiling- 
point  and  the  pressure,  for  example  b.  p.  22  145°.  The  tem- 
perature of  the  bath  should  also  be  recorded  for  reference. 

It  is  not  always  possible  to  obtain  exactly  the  same  pressure 
at  which  the  boiling-point  is  given  in  the  text.  However,  the 
difference  in  boiling-points  at  the  given  pressure  and  the  pressure 
actually  used  can  be  estimated.  The  distillate  is,  of  course, 
always  collected  while  the  temperature  (and  pressure)  remains 
constant. 

There  is  no  set  rule  or  exact  method  of  calculation  for  finding 

the  boiling-point  under   diminished  pressure   when   only   the 

boiling-point  at  760  mm.  is  known.     A  few  general  hints  may  be 

given.    A  substance  that  boils  around  100°  at  760  mm.  will 

i  boil  about  60°  lower  at  25  mm.,  and  one  that  boils  around  200° 

!  at  760  mm.  will  boil  about  8o°-ioo°  lower  at  25  mm.     The 

variation  in  the  boiling-point  becomes  greater  for  each  degree 

:  at  the  lower  pressure,  and  is  very  marked  as  the  pressure  drops 

below  3  or  4  mm. 

NOTES 

1.  Purification  of  mercury:    If  the  mercury  is  wet  or  dirty  it  can  be 
purified  by  running  it  through  a  dry  filter  paper  which  has  a  pin  hole 
in  the  bottom.    The  impurities  stick  to  the  paper,  which  also  absorbs 
the  moisture.    Several  treatments  may  be  necessary  with  clean  filters 
each  time.  \ 

2.  If  the  water  pump  does  not  "catch,"  and  the  water  runs  out 
straight  without  causing  proper  suction,  hold  the  hand  close  to  the 
bottom  of  the  pump  while  the  water  is  turned  on  and  cause  a  slight 
back  pressure  until  the  suction  is  all  right. 

3.  Never  use  an  ordinary  flat-bottomed  flask  in  the  apparatus 
for  vacuum  distillation.    Explain. 

1  Tap  the  glass  tubing  before  taking  the  reading  in  order  to  bring  the  mercury 
to  rest  and  overcome  the  "lag." 


82  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

4.  Sometimes  for  more  complete  cooling  a  water  condenser  must 
be  placed  between  the  distilling-flask  and  the  receiver. 

5.  An  apparatus  for  collecting  fractions  without  interrupting  the 
distillation  is  described  by  M.  T.   Bogert,  Journ.  Ind.  \and  Eng. 
Chem.,  7  (1915),  785-6. 

6.  If  water  should  splash  into  the  oil,  the  distillation  must  be 
stopped  and  the  wet  oil  replaced  with  fresh  oil.     If  this  happens 
while  the  oil  is  hot  it  will  foam  very  much  and  great  care  must  be 
used  to  prevent  any  of  the  hot  oil  from  getting  on  your  hands,  etc. 
Oil  with  even  a  very  small  amount  of  water  in  it  is  useless. 

QUESTIONS 

1.  In  "  vacuum  distillation  "  how  is  bumping  avoided? 

2.  Why  should  the  outlet  tube  of  the  distilling-flask  extend 

into  the  bulb  of  the  receiver? 

3.  Why  should  the  distilling-flask  be  not  more  than  one- third 

full? 

4.  Why  is  the  stop-cock  opened  before  the  water  is  turned  off? 

5.  Why  is  the  tube  from  the  suction  flask  to  the  pump  run 

down  to  the  bottom  of  the  suction  flask? 

6.  What  advantages  has   a   Claisen  flask  in  distillation    i 

vacua? 

7.  Why  should  an  ordinary  flat-bottomed  flask  never  be  used 

in  the  apparatus  for  vacuum  distillation? 

8.  How  low  a  pressure  can  be  obtained  with  a  water  pump? 

9.  Why  is  it  not  necessary  to  have  an  absolutely  definite 

volume  of  mercury  in  the  tube? 

10.  Do  air  bubbles  along  the  walls  make  any  difference? 

11.  Does  the  mercury  drop  exactly  as  far  as  it  rises? 

12.  Which  reading  on  the  barometer  should  you  use  for  calcula- 

ting the  pressure  within  the  apparatus,  the  "  corrected  " 
or  "  uncorrected  "? 


Experiment  No.  16 

OXIDATION  OF  A  PRIMARY  ALCOHOL  TO  AN  ALDEHYDE 
Preparation  of  a  Solution  of  Acetaldehyde 

In  this  experiment  ethyl  alcohol  is  oxidized  to  acetaldehyde 
by  means  of  sodium  dichromate  in  dilute  sulfuric  acid  solution. 
Since  it  is  difficult  to  separate  the  acetaldehyde,  which  boils  at 
21°,  from  the  impurities  by  fractionation,  the  crude  acetaldehyde 
is  usually  absorbed  in  ether  and  converted  into  the  crystalline 
aldehyde  ammonia,  which  is  easily  purified,  and  then  used  for 
making  pure  acetaldehyde.  This  is  a  long  process,  however,  and 
requires  elaborate  apparatus,  as  described  in  Expt.  17. 

For  making  a  crude  product  which  can  be  used  in  the  alde- 
hyde tests,  proceed  as  follows: 

Attach  a  dropping-funnel  to  a  25o-cc.  distilling-flask  con- 
nected with  a  long  water  condenser,  and  arrange  a  receiver  set 
in  ice.  On  account  of  its  low  boiling-point  care  must  be  exer- 
cised in  catching  the  distillate.  A  small  Erlenmeyer  flask  makes 
a  good  receiver.  The  end  of  the  condenser  should  extend  into 
it  as  far  as  possible  and  the  flask  should  be  entirely  surrounded 
^Ueer^  Add  a  mixture  of  20  cc.  of  cone,  sulfuric  acid  and  50  cc. 
of  water.,  Fill  the  dropping-funnel  with  a  solution  of  20  grams  of 
sodium  dichromate  in  30  cc.  of  water  and  25  cc.  of  alcohol,  and 
during  the  course  of  about  fifteen  to  twenty  minutes  allow  this 
to  drop  slowly  into  the  flask.  Heat  the  mixture  to  gentle  boiling 
with  a  very  small  flame.  After  all  the  solution  has  been  added 
continue  the  gentle  heating  for  several  minutes.  Redistill  very 
slowly,  collecting  the  portion  boiling  between  20°  and  45°  in  an 
ice-cooled  receiver.  Acetaldehyde  boils  at  21°.  The  product 
(which  need  not  be  handed  in)  contains  some  water,  but  can  be 
used  in  the  experiments  entitled  "  Tests  for  Aldehydes,"  Expt. 

83 


84  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

19,  p.  91.     For  study,  use  the  questions  given  under  the  prepara- 
tion of  acetaldehyde  from  aldehyde  ammonia,  Expt.  No.  18,  p.  90. 

NOTE 

This  experiment  and  the  tests  which  follow  should  if  possible  be 
carried  out  during  one  laboratory  period.     Otherwise   extra  pre 
cautions  must  be  taken  to  keep  the  solution  of  the  aldehyde  properly 
stoppered  and  cooled. 


Experiment  No.  17 

OXIDATION  OF  A  PRIMARY  ALCOHOL  TO  AN  ALDEHYDE 
The  Preparation  of  Acetaldehyde  Ammonia 

In  this  experiment  ethyl  alcohol  is  oxidized  to  acetaldehyde 
by  means  of  sodium  dichromate  in  dilute  sulfuric  acid  solution. 
Since  it  is  difficult  to  'separate  the  acetaldehyde,  which  boils  at 
21°,  from  the  impurities  by  fractionation,  the  crude  acetaldehyde 
is  absorbed  in  ether  and  converted  into  the  crystalline  aldehyde 
ammonia,  which  is  easily  purified,  and  then  used  for  preparing 
pure  acetaldehyde. 

Set  up  the  following  apparatus  and  have  it  ready  to  start  the 
experiment  at  the  beginning  of  the  laboratory  period.  If  the 
j  experiment  cannot  be  completed  in  one  period,  it  must  at  least  be 
continued  until  the  aldehyde  has  all  been  absorbed  in  ether 
(one  hour)  which  solution  can  then  be  set  aside  in  the  icebox 
in  a  well-stoppered  bottle. 

To  a  500  cc.  flask  attach  an  addition  tube  (Fig.  3,  p.  13), 
insert  a  dropping-funnel  (Fig.  6,  p.  36),  and  connect  the  side 
arm  with  a  long  slanting  reflux  condenser  (60  cm.).  Through 
a  cork  in  the  upper  end  of  the  condenser  attach  a  bent  tube  and 
connect  this  with  a  100  cc.  pipette  leading  into  a  250  cc.  wide- 
mouthed  bottle  (with  a  vent)  set  in  an  ice  mixture.  Place  a 
thermometer  inside  the  inner  tube  of  the  condenser  and  support 
it  with  a  thread  held  fast  by  the  cork  stopper  at  the  upper  end. 
The  bulb  of  the  thermometer  should  be  as  near  the  center  of  the 
condenser  as  possible.  Insert  another  thermometer  through  the 
stopper  at  the  upper  end  in  order  that  the  temperature  of  the 
issuing  vapors  may  be  noted.1  Use  good  corks  and  make 

1  A  second  addition  tube  can  be  used  here  also  if  desired. 
85 


86  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

tight  connections  throughout.     Rubber  stoppers  may  be  used 
with  advantage. 

Into  the  bottle  surrounded  by  ice  pour  100  cc.  of  anhydrous 
ether.  The  pipette  should  open  about  i  cm.  below  the  surface 
of  the  ether.  Add  a  mixture  of  17  cc.  of  cone,  sulfuric  acid  and 
75  cc.  of  water  to  the  flask,  and  during  the  course  of  thirty 
minutes  allow  a  solution  of  35  grams  of  sodium  dichromate 
in  60  cc.  of  water  and  50  cc.  of  alcohol  to  drop  in  slowly.  During 
this  time  heat  the  solution  to  gentle  boiling,  and  allow  the 
water  to  run  very  slowly  through  the  condenser.  Regulate 
the  heat  and  water  flow  so  that  the  temperature  indicated  by 
the  thermometer  in  the  condenser  does  not  register  higher  than 
45°.  (What  is  the  lowest  temperature  limit?  1  Why  must  a 
large  flame  not  be  used?)  After  all  the  mixture  has  been  added 
continue  the  heating  with  the  same  precautions  for  an  additional 
thirty  minutes.  If  the  ether  solution  at  any  time  should  rise  j 
high  in  the  pipette,  add  a  little  more  of  the  solution,  or  if  this 
has  all  been  added  simply  open  the  stop-cock  of  the  dropping-  '[ 
funnel  momentarily.  All  the  aldehyde  has  been  driven  over 
when  its  pungent  odor  is  not  very  strong  in  the  funnel  opened 
for  the  test. 

When  the  apparatus  is  disconnected  note  the  most  pronounced 
odor  from  the  mixture  in  the  flask.  To  what  is  this  due?  How 
can  you  account  for  it? 

Through  a  wide  tube,  such  as  the  large  part  of  a  calcium 
chloride  tube  or  an  adapter,  or  a  funnel,  pass  a  stream  of  an- 
hydrous ammonia  from  a  cylinder  into  the  ether  solution  con- 
tained in  the  wide-mouthed  bottle  packed  in  ice  and  salt  near 
the  draft  pipe.  The  solution  will  be  saturated  in  about  five 
minutes.  Filter  off  the  white  crystals  of  aldehyde  ammonia  with 
suction  and  dry  them  until  all  the  ether  has  completely  evapo- 
rated. This  can  be  done  conveniently  in  a  vacuum  desiccator. 
The  aldehyde  ammonia  is  somewhat  soluble  in  ether  and  a  second 
crop  of  crystals  can  be  obtained  by  concentrating  the  mother 


1  In  wintertime  warm  water  should  be  added  to  the  condenser  to  bring  the 
temperature  within  the  proper  limits. 


LABORATORY  EXPERIMENTS  87 

liquor.  Determine  the  melting-point.  Yield,  13  grams.1  The 
aldehyde  ammonia  often  becomes  yellow  and  brown  on  standing 
and  loses  its  crystalline  character,  probably  due  to  slow  "  resin- 
ification."  For  this  reason  the  product  should  not  be  allowed 
to  remain  in  the  desiccator  more  than  a  day.  This  chemical 
change  can  be  noted  by  the  lowering  of  the  melting-point. 

NOTES 

1.  In  case  an  addition  tube  is  not  at  hand,  use  a  two-holed  stopper 
through  which  pass  the  stem  of  the  dropping-funnel  and  the  small 
end  of  an  adapter.    The  condenser  is  then  connected  with  the  adapter. 

2.  If  an  ammonia  cylinder  is  not  available,  the  dry  ammonia 
gas  can  be  obtained  by  boiling  the  ordinary  cone,  ammonium  hydrox- 
ide solution,  sp.  gr.  0.90,  and   passing  the  vapors  through  a  drying 
tower  containing  calcium  oxide,  care  being  taken  that  a  wide  tower 
is  used. 

3.  Vacuum  desiccator.    A  vacuum  desiccator  is  like  an  ordinary 
desiccator,  but  has  as  top-cock  on  a  ground-in  stopper  in  the  cover. 
Put  some  calcium  chloride  or  cone,  sulfuric  acid  in  the  bottom  and 
place  the  watch  glass  containing  the  substance  on  a  support,  such  as  a 
perforated  porcelain  disk  or  a  wire  gauze,  across  the  constricted  part 
of  the  desiccator.  Grease  the  stop-cock,  and  the  other  ground  surfaces. 
Attach  the  outlet  to  the  suction  with  a  heavy  rubber  tube,  open  the 
stop-cock  and  evacuate.    15-30  minutes  usually  suffices.    Close  the 
stop-cock  and  then  remove  the  rubber  tube  before  shutting  off  the 
suction  (?).    When  ready  to  open  the  desiccator  turn  the  stop-cock 
just  enough  to  let  in  the  air  slowly,  otherwise  the  rush  of  air  may 
blow  the  dry  particles  about. 

It  is  well  to  insert  a  stout  empty  bottle  in  the  connection  between 
the  desiccator  and  the  pump.  Then  if  there  is  any  back  pressure 
and  the  water  begins  to  flow  back  it  will  be  caught  in  the  bottle  and 
you  will  have  time  to  disconnect  before  it  reaches  the  desiccator. 

Never  go  away  and  allow  the  stop-cock  to  remain  open  with  the 
suction  on,  especially  when  a  water-pump  is  used.  The  change  in 
water  pressure  may  cause  the  water  to  be  drawn  in  and  flood  the 
desiccator. 

1  This  amount  is  too  bulky  for  the  usual  preparation  bottle.  Hand  in  a 
sample,  stating  the  total  yield  on  the  label,  and  use  the  major  portion  for  the 
preparation  of  acetaldehyde  itself  in  the  next  experiment, 


88  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

Liquids  will  evaporate  about  six  to  seven  times  faster  in  a  vacuum 
desiccator  than  in  an  ordinary  desiccator,  as  shown  recently  by  Mr. 
W.  E.  Morgan. 

The  efficiency  of  the  conventional  vacuum  desiccator  can  be 
increased  if  it  is  provided  with  a  second  inlet  tube,  with  stop-cock 
attached,  in  the  lower  part  of  the  desiccator.  While  the  suction  is 
on,  allow  air,  which  is  thoroughly  dried  by  passage  through  some  of 
the  same  kind  of  drying  agent  used  within  the  desiccator,  to  enter 
very  slowly  through  this  inlet  tube. 

QUESTIONS 

1.  Write  equations  for  all  the  chemical  changes  involved  in  the 

formation  of  acetic  aldehyde  from  ethyl  alcohol  by  this 
method. 

2.  Point  out  in  the  above  reactions  what  is  oxidized  and  what 

is  reduced. 

3.  Why  cannot  a  simple  water  solution  of  sodium  dichromate 

be  used  instead  of  one  that  has  been  acidified  with  sul- 
furic  acid? 

4.  What    causes    the    green    coloration?     (Compare  Mellor, 

"  Modern  Inorganic  Chemistry  "  (1912),  652.) 

5.  Could  hydrochloric  or  acetic  acid  be  used  in  place  of  sul- 

furic  acid? 

6.  Why  is  a  dropping-funnel  necessary?    Why  not   add  the 

mixture  of  dichromate  and  alcohol  all  at  one  time? 

7.  Why  not  omit  heating  the  mixture  in  the  reaction  flask  until 

after  the  alcohol  and  the  dichromate  has  all  been  added? 

8.  Why  is  the  condenser  attached  to  the  reaction  flask  held  in 

a  slanting  position? 

9.  Why  is  it  important  to  keep  the  temperature  of  the  condenser 

at  about  45°? 

10.  Why  is  it  necessary  to  absorb  the  acetic  aldehyde  in  anhy- 

drous ether?    Why  is  water  not  used  in  place  of  ether? 
Alcohol? 

11.  Why  is  it  necessary  to  keep  the  ethereal  solution  of  the 

aldehyde  cold? 

12.  How  does  anhydrous  ammonia  react  with  acetic  aldehyde? 

Write  equation. 

13.  Do  all  aldehydes  react  in  a  similar  way  when  treated  with 

anhydrous  ammonia?     Compare  formaldehyde  and  benz- 
aldehyde. 

14.  How  does  water  react  with  formaldehyde? 


LABORATORY  EXPERIMENTS 


15.  Could  aqueous  ammonia  be  used  in  place  of  tne  anhydrous 

ammonia? 

1 6.  Why  is  a  wide  tube  used  to  pass  the  ammonia  gas  into  the 

ethereal  solution? 

17.  Explain  how  a  mixture  of  ice  and  salt  is  colder  than  ice  alone. 

18.  What  advantage  does  a  vacuum  desiccator  have  over  an 

ordinary  desiccator  for  drying  these  crystals? 

19.  What  impurities  are  liable  to  contaminate  the  crystals  of 

aldehyde  ammonia?     Name  four  and  account  for  them. 

20.  Since  the  object  of  making  the  aldehyde  ammonia  is  not  only 

to  show  the  formation  of  the  addition  product  but  also  to 
obtain  pure  acetaldehyde,  why  not  make  the  pure  acetalde- 
hyde  directly  by  simply  catching  the  main  distillate  in  a 
flask  in  a  freezing-mixture  and  then  fractionating  this? 


Experiment  No.  18 
The  Preparation  of  Acetaldehyde  from  Aldehyde  Ammonia 

From  the  aldehyde  ammonia  (which  should  be  entirely  free 
from  ether)  prepared  in  the  preceding  experiment  prepare  acet- 
aldehyde  as  follows:  Provide  a  distilling-flask  with  a  dropping- 
funnel,  connect  with  a  condenser  and  attach  to  the  latter  a  tube 
leading  to  the  bottom  of  a  second  distilling-flask  which  is  set  in  a 
mixture  of  ice  and  salt.  Dissolve  10  grams  of  aldehyde  ammonia 
in  25  cc.  of  water  and  allow  tkis  to  drop  into  a  solution  of  8  cc. 
of  cone,  sulfuric  acid  in  20  cc.  of  water  in  the  distilling-flask 
heated  with  boiling  water.  Dry  the  distillate  with  calcium 
chloride  in  the  flask  in  which  it  was  collected  by  shaking  for 
a  few  minutes,  and  then  distill  from  this  same  flask  without 
removing  the  calcium  chloride,  using  the  precautions  noted  above. 
Pure  acetaldehyde  boils  at  20.8°  cor.  Use  the  product  in  the 
following  experiments.  (Keep  the  product  in  a  well-stoppered 
bottle  in  the  ice-box  if  it  is  not  used  on  the  same  day  it  is  made.) 

QUESTIONS 

1.  Write  all  equations  for  reactions  involved  in  the  formation 

of  the  aldehyde  from  its  aldehyde  ammonia. 

2.  Why  should  the  aldehyde  ammonia  used  be  entirely  free  from 

ether? 

3.  Why  is  the  aldehyde  ammonia  dissolved  in  water  before 

being  added  to  the  dilute  sulfuric  acid? 

4.  Why  should  the  end  of  the  condenser  be  extended  to  the 

bottom  of  a  small  distilling  flask? 

5.  Why  is  this  distilling  flask  surrounded  by  a  freezing  mixture? 

6.  Why  is  it  necessary  to  redistill  the  aldehyde? 

7.  Could  any  other  drying  agent  besides  calcium  chloride  be 

used  for  drying  the  acetic  aldehyde? 

8.  What  advantage  has  the  porous  calcium  chloride  over  fused 

stick  calcium  chloride  in  this  case? 

9.  Why  is  the  drying  agent  not  removed  before  the  distillation 

in  this  case  while  in  practically  all  other  experiments  the 
drying  agent  is  removed  before  the  distillation? 

90 


Experiment  No.  19 
Tests  for  Aldehydes 

1.  Silver-mirror   test.      Make   an   ammoniacal   solution   of 
silver  nitrate  by  treating  4  cc.  of  N/io  silver  nitrate  with  3N 
ammonium  hydroxide  drop  by  drop  until  the  precipitate  (?) 
which  is  first  formed  just  redissolves.     Add  a  single  drop  of  the 
aldehyde,  quickly  mix  by  shaking,  and  set  the  tube  in  the  rack. 
A  deposit  of  metallic  silver  will  begin  to  form  at  once  and  soon 
makes  a  beautiful  mirror.     If  the  test-tube  is  not  perfectly 
clean  only  a  black  precipitate  of  silver  will  be  obtained.     If 
necessary,  clean  the  tube  with  boiling  sodium  hydroxide  solu- 
tion. \ 

Sometimes  a  very  small  amount  of  dilute  sodium  hydroxide 
solution  must  be  added  in  order  to  get  the  reduction.  Com- 
pare Benzaldehyde  experiment,  p.  182.  A  mixture  of  sodium 
hydroxide  and  silver  nitrate  constitutes  Tollens'  reagent  for 
aldehydes. 

Do  not  heat  the  silver  solution  or  let  it  stand  for  a  long 
time,  since  explosive  compounds  are  formed.  See  Smith,  "  In- 
org.  Chem.,"  p.  753;  Alfred  Tingle,  "  Ammoniacal  Silver  oxide 
Solution,"  Journ.  Ind.  and  En g.  Chem.,  11  (1919),  379;  and  E.  J. 
Witzemann,  ibid.,  11  (1919),  893;  also,  note,  884. 

2.  Reduction  of  Fehling's  Solution.     Mix  3  cc.  of  each  of  the 
two  portions  of  Fehling's  Solution  ("  copper  half  "  and  "  alka- 
line tartrate  half  "),  and  bring  the  clear,  deep  blue  solution  to  a 
boil.    Note  whether  a  precipitate  is  formed.     If  not,  add  a 
drop  of  the  aldehyde  and  boil  for  a  minute.     A  yellow  precipitate 
of  cuprous  hydroxide  is  generally  formed  at  first  and  this  is 
rapidly  converted  into  bright  red  cuprous  oxide.    If  the  amount 
of  reduction  is  small  the  cuprous  oxide  sometimes  cannot  be  seen 
until  after  the  solution  has  been  allowed  to  stand  long  enough 
for  it  to  settle  out.     Or  the  solution  can  be  filtered.    Note  the 
odor  during  the  boiling,  and  compare  test  4. 

91 


92  LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

Fehling's  solution  is  kept  in  two  parts  because  it  gradually 
deteriorates  on  standing  after  being  mixed. 

3.  Polymerization.    To  a  little  of  the  aldehyde  add  a  single 
drop  of  cone,  sulfuric  acid  on  a  stirring  rod.     (Care!)     What  is 
formed? 

4.  Resin  Formation.     Gently  heat  a  little  aldehyde  and  a 
few  drops  of  a  cone,  solution  of  sodium  hydroxide.     (?) 

5.  Schiff's  Aldehyde  Test.     SchifT's   aldehyde  reagent  con- 
sists of  a  very  dilute  solution  of  fuchsine  decolorized  with  sul- 
furous  acid.     It  is  also  known  as   "  Fuchsine-sulfurous  acid 
reagent,"  and  is  furnished  ready  for  use  by  the  stockroom. 

Add  a  drop  of  the  aldehyde  to  5  cc.  of  water  and  then  add 
a  drop  of  the  reagent.  The  development  of  the  original  reddish- 
violet  color  of  the  fuchsine  indicates  the  presence  of  an  alde- 
hyde. 

Schiff's  reagent  can  be  prepared  by  dissolving  0.2  gram  of 
pure  fuchsine  or  rosaniline  (in  the  form  of  the  hydrochloride  or 
acetate)  in  1 5  cc.  of  water  and  passing  in  sulfur  dioxide  until  the 
solution  is  saturated.  This  requires  but  a  few  minutes  and 
the  solution  will  be  colorless,  provided  pure  rosaniline  or  its 
salt  were  used.  Then  dilute  to  200  cc.  It  should  be  kept  in  a 
dark-colored  glass-stoppered  bottle.  If  the  bottle  is  not  properly 
stoppered  the  liquid  will  gradually  lose  sulfur  dioxide  and  then  ! 
of  course  the  color  will  return  even  before  any  aldehyde  is  added. 

Do  not  boil  the  reagent!  Why?  What  would  happen  if 
a  weakly  alkaline  substance  was  added  to  the  reagent? 

The  reactions  in  the  SchifT's  Aldehyde  Test  are  not  completely 
understood.  The  manner  in  which  the  aldehyde  removes  the 
sulfurous  acid  is  probably  similar  to  the  reaction  of  an  aldehyde 
and  sodium  bisulfite.  See  Acetone,  p.  98. 

QUESTIONS 

1.  Discuss  the  reactions  involved  when  the  acetic  aldehyde  is 

mixed  with  ammoniacal  silver  nitrate. 

2.  What  is  the  purpose  of  the  alkali  in  this  test  for  aldehydes? 

(Stieglitz,  "  Qualitative  Chemical  Analysis,"  I,  290-2.) 

3.  Is  it  necessary  to  employ  the  nitric  acid  salts  for  this  oxida- 


LABORATORY  EXPERIMENTS  93 

tion  of  the  aldehyde,  or  could  silver  acetate  be  used  just 
as  well? 

What  advantage  does  Fehling's  solution  have  over  an  ordi- 
nary aqueous  solution  of  copper  sulfate  in  testing  for 
aldehydes? 
How  is  heating  advantageous  in  the  Fehling's  solution  test 

for  aldehydes? 

6.  In   the   polymerization   of   acetic   aldehyde   by   means   of 
sulfuric  acid,  why  is  it  necessary  to  add  only  a  trace 
of  acid  instead  of  a  drop? 
Why  is  it  best  to  cool  the  aldehyde  with  a  freezing  mixture 

before  adding  the  acid? 
Write  equation  and  structures  in  the  reactions  involved 

in  the  polymerization  of  the  aldehyde  by  acid. 
9.  Is  the  above  reaction  reversible? 

o.  Write  equations  and  structures  for  reactions  which  take 
place  when  acetic  and  formic  aldehydes  are  each  treated 
with  cone,  and  with  dil.  solutions  of  sodium  hydroxide. 


Experiment  No.  20 

HYDROLYSIS  OF  METHYLENE  DIETHERS  (ACETALS) 
Methylal1 

1.  Does  its  odor  resemble  that  of  the  ethers?     To  what 
alcohols  are  these  ethers  related? 

2.  To  3  drops  of  methylal  in  a  test-tube  add  2  drops  of  cone, 
sulfuric  acid.     Heat  gently  over  a  small  flame  until  the  liquid 
begins  to  boil,  and  then  allow  to  cool.     What  is  the  white  solid 
that  is  deposited  on  the  walls  of  the  tube?    Note  the  odor  of  the 
gas  evolved.     (Care!)     Outline  the  "steps"  in  the  reactions  of 
this  experiment. 

3.  Repeat  the  above  experiment,  using  dilute  sulfuric  acid. 
Any  white  solid  formed?    Odor? 

4.  Try  the  action  of  dilute  sodium  hydroxide  solution  on 
methylal.     (?) 

5.  What  is   an   ortho-ester? 2     What  is   formed   when   an 
ortho-ester  is  warmed  with  an  alcoholic  solution  of  potassium 
hydroxide? 

6.  Does  methylal  reduce  Fehling's  solution,  or  ammoniacal 
silver  nitrate?     (See  under  Acetaldehyde,  p.  91.) 


chemical 


QUESTIONS 

Write    equations    for   reactions    involved   m   the 

change  produced  by  the  action  of  cone,  sulfuric  acid  on 
methylal. 

What  is  polymerization?  Show  by  structure  how  this  polym- 
erization of  formaldehyde  to  paraldehyde  differs  from  a 
polymerization  like  formaldehyde  to  formose. 

1  Methylal  boils  at  42°. 

2  Richter's  "Organische  Chemie,"  u.  Auflage  (1909),  Vol.  I,  273,  316. 

94 


LABORATORY  EXPERIMENTS  95 

3.  What  is  the  structure  of  the  formaldehyde  in  the  water 

solution  obtained  when  dil.  sulfuric  acid  reacts  with  the 
methylal? 

4.  How  is  methylal  formed?    Two  methods. 

5.  Show  how  it  is  related  to  ethers  by  its  behavior  when  hydro- 

lyzed. 

6.  Can  diethyl  ether  be  hydrolyzed  by  sulphuric  acid? 

7.  Can  aqueous  alkali  cause  hydrolysis  of  methylal  or  ethyl  ether? 

8.  Of  what  alcohol  is  methylal  an  ether?     Does  it  exist?     Cont 

pare  chloral  hydrate. 


Experiment  No.  21 
Formaldehyde 

1.  Dissolve  2  drops  of  methyl  alcohol  in  3  cc.  of  water  in  a 
small  test-tube  (No.  i).     Make  a  compact  spiral  of  fine  copper 
wire  by  winding  it  around  a  glass  rod.     The  spiral  should  be  about 
2  cm.  long  and  should  have  a  straight  piece  about  20  cm.  long. 
Oxidize  the  spiral  by  moving  it  rapidly  through  a  Bunsen  flame, 
and  plunge  the  red-hot  wire  into  the  alcohol  solution.     Repeat 
this  operation  several  times. 

Pour  the  solution  from  the  solid  .particles  into  another  small 
test-tube,  and  add  i  drop  of  a  fresh  0.5  per  cent  solution  of  re- 
sorcinol.1  Carefully  pour  this  solution  down  the  sides  of  a  second 
test-tube  containing  about  5  cc.  of  cone,  sulfuric  acid.  If  the 
second  tube  is  properly  inclined  the  mixture  will  form  a  distinct 
layer  upon  the  surface  of  the  acid. 

A  red  zone,  slightly  violet  in  color,  will  appear,  and  above  the 
zone  there  will  be  a  light  flocculent  precipitate.  This  reaction 
is  characteristic  of  formaldehyde ;  other  aldehydes  do  not  show 
this  behavior.  The  composition  of  the  colored  substance  and 
of  the  precipitate  is  not  well  understood. 

(Reprinted  with  permission  from  Jones,  "  A  Laboratory  Outline  of  Organic 
Chemistry,"  p.  25.} 

2.  Evaporate  5  cc.  of  "  formalin  "  (commercial  40  per  cent 
solution  of  formaldehyde)  to  dryness  on  the  water-bath,  under 
the  hood.     What  is  the  residue? 

3.  Preparation   of   Hexamethylenetetramine.     In   a   round- 
bottomed  flask  mix  25  cc.  of  "  formalin  "  and  15  cc.  of  cone. 

1  If  the  resorcinol  solution  is  allowed  to  stand  for  some  time  it  gradually  develops 
a  brownish  flocculent  precipitate,  and  then  it  is  worthless  for  this  test. 

96 


LABORATORY  EXPERIMENTS  97 

ammonium  hydroxide.  Insert  an  inlet  tube  drawn  out  to  a  cap- 
illary at  the  lower  end  and  opening  near  the  bottom  of  the  flask, 
and  an  outlet  tube  connected  with  a  suction  flask,  stop-cock, 
and  water  pump,  and  evaporate  approximately  to  dryness  in 
vacua  (compare,  Expt.  15,  p.  76),  over  the  steam-bath,.  By 
attaching  a  piece  of  rubber  tubing  with  a  screw  clamp  to  the 
inlet  tube  the  stream  of  bubbles  can  be  regulated.  Then  add 
a  second  portion  of  ammonium  hydroxide  and  evaporate  again. 

Dissolve  out  the  residue  with  hot  absolute  alcohol  and  filter 
while  hot.  The  hexamethylenetetramine  crystallizes  out  of  the 
nitrate  in  colorless,  well-formed  rhombohedra.  The  crystals 
should  of  course  be  filtered  off  before  the  solution  is  allowed  to 
evaporate  to  a  small  bulk  since  the  mother  liquor  contains  a 
considerable  amount  of  by-products  as  impurities.  The  sub- 
stance sublimes  when  heated,  and  is  very  soluble  in  water. 

It  is  used  in  medicine,  usually  under  the  name  of  "  urotro- 
pine,"  also  for  preparing  condensation  products  of  phenols 
(Bakelite),  for  absorbing  poisonous  gases,  in  gas-masks,  as  an 
"  accelerator  "  (catalyst)  in  the  vulcanization  of  rubber,  etc. 

QUESTIONS 

1.  Explain  the  formation  of  formaldehyde  from  methyl  alcohol. 

2.  What  is  "  formalin  "?     How  prepared  commercially? 

3.  What  is  obtained  when  the  "  formalin  "  evaporates  to  dry- 

ness? 

4.  What  is  trioxymethylene?    For  what  is  it  used  in  commerce? 

5.  Write    the   formula   proposed   for   hexamethylenetetramine. 

(Richter's    "  Organic    Chemistry,"    trans,  by  Spielmann, 
Vol.  I,  p.  211.) 

6.  Compare  the  action  of  ammonia  on  formaldehvde,  acetalde- 

hyde  and  benzaldehyde. 


O 


Experiment  No.  22 
Acetone 


1.  Mix  5  cc.  of  acetone  with  7  cc.  of  a  saturated  solution  of 
sodium  bisulfite.1     Shake  vigorously.     Note  the  heat  developed. 
What  is  the  product  that  separates?    How  may  acetone    be 
regenerated  from  it?    How  is  this  reaction  used  in  analysis? 
Do  all  ketones  respond  to  this  test?    How  does  KCN  react  with 
the  bisulfite  addition  product? 

2.  Try  the  action  of  the  fuchsine-sulfurous  acid  reagent  on 
acetone.     (?) 

3.  Does  acetone  reduce  Fehling's  solution,  or  an  ammoniacal 
solution  of  silver  nitrate? 

*4.  Write  the  structure  of  dibenzalacetone  (dibenzylidene 
acetone).  (Compare  Perkin  and  Kipping,  " Organic  Chemistry,". 
p.  456.)  How  can  it  be  formed?  Explain  the  reaction  for  its 
preparation.  What  is  its  significance  in  organic  analytical  chem- 
istry? 

5.  How  can  you  prepare  iodoform  from  acetone?  Is  this 
reaction  characteristic  of  most  ketones  which  contain  the 
CH3CO  group? 

1  The  saturated  solution  of  sodium  bisulfite  is  prepared  by  means  of  sodium 
hydroxide  solution  and  sulfur  dioxide,  or  by  passing  sulfur  dioxide  into  a  mixture 
of  sodium  bicarbonate  in  three  parts  of  water  until  the  solution  smells  strongly  of 
the  gas.  On  long  standing  unless  properly  stoppered  it  is  slowly  converted  into 
the  sulfate.  This  can  generally  be  noticed  by  loss  of  the  yellowish  color  of  the 
saturated  solution  and  by  the  presence  of  a  white  sediment.  It  will  then  no  longer 
give  the  crystalline  addition-product  with  acetone,  etc. 

*  Need  not  be  studied  by  students  in  the  "short"  course. 


98 


Experiment  No.  23 

FORMATION  OF  A  KETONE  BY  THE  OXIDATION  OF  A  SECONDARY 
ALCOHOL  AND  THE  FORMATION  OF  A  KETOXIME 

Preparation  of  /-Menthone  from  /-Menthol 

Pour  3  cc.  (no  more)  of  cone,  sulfuric  acid  into  40  cc.  of 
water  and  dissolve  5  grams  of  sodium  dichromate  in  this  solution. 
Transfer  to  a  small  glass-stoppered  bottle,  and  add  5  grams  of 
powdered  /-menthol.  Shake  frequently  during  the  next  half 
hour  and  let  stand  overnight  or  longer.  When  the  mixture 
is  allowed  to  stand  the  solid  lumps  should  be  in  contact  with 
the  liquid  and  not  sticking  to  the  walls  of  the  bottle  above 
the  liquid.  These  dark-colored,  insoluble  masses  probably  con- 
sist of  the  ester  of  menthol  and  chromic  acid  which  is  first 
formed,  and  they  gradually  disappear,  leaving  a  dark  but  clear 
solution  with  the  menthone  floating  as  an  oil  on  the  surface. 
Extract  the"  mixture  in  a  separatory  funnel  with  about  25  cc. 
of  ether.  Filter  the  ether  solution  into  a  small  weighed  beaker 
and  evaporate  the  ether  by  means  of  warm  water.  Support 
an  inverted  funnel  over  the  beaker  and  connect  with  the  suction 
to  carry  away  the  ether  vapors.  As  soon  as  the  fumes  of  ether 
iare  no  longer  evident  as  shown  by  the  odor,  cool  and  then 
determine  the  yield  of  crude  menthone  (about  4.5  grams).  It  is 
somewhat  volatile  at  the  ordinary  temperature  and  pressure, 
and  therefore  it  should  not  be  heated  too  long. 

An  excess  of  sulfuric  acid  must  be  avoided  since  it  gradually 
changes  the  levo-compound  into  the  dextro-variety.  Menthone 
-  is  one  of  the  chief  constituents  of  the  oil  of  peppermint.  It 
is  a  colorless  liquid  boiling  at  109°  at  36  mm. 

It  need  not  be  further  purified  for  the  following  experiment. 

99 


100          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 


Preparation  of  /-Menthone  Oxime  from  /-Menthone 

Dissolve  2  grams  of  the  crude  menthone  in  three  times  its 
weight  of  about  90  per  cent  alcohol  (sp.  gr.,  approximately  0.83) 
in  a  small  beaker  (No.  oo).    Add  an  amount  of  powdered  hydrox- 
ylamine  hydrochloride  equal  to  1.3  times  the  theoretical  amount 
required   by   the   equation.     It   will   not   all   dissolve.     Then, 
during  ten  minutes,  add  in  portions  with  stirring,  slightly  more 
than  the  theoretical  quantity  of  sodium  hydrogen  carbonate 
required    to    neutralize    the    hydrochloric    acid    of    the    first  | 
salt  and  free  the  hydroxylamine.     Let  stand  for  thirty  minutes 
with  occasional  stirring.     Pour  the  mixture  into  75  cc.  of  cold  | 
water  and  stir  vigorously.     The  oxime  separates  immediately  | 
as  an  oil  or  a  white  semi-solid  mass  which  soon  solidifies.     Cool 
further  if  necessary  to  help  solidification.     Filter  with  suction.  1 
Dissolve  the  product  in  hot,  approximately  50  per  cent  alcohol, 
50  cc.  for  each  gram,  filter  while  hot  if  necessary  to  remove  ] 
any  insoluble  particles,  and  set  aside  for  crystallization.     Before 
setting  aside  cover  the  beaker  with  a  watch  glass.     After  the  first 
crop  of  crystals  has  been  filtered  off  a  second  may  often  be 
obtained  by  longer  standing.     White  needles  of  a  characteristic 
persisting  odor  are  obtained  which  melt  at  60°.     The  product 
may  be  dried  by  letting  it  stand  overnight  on  a  clean  porous 
tile  covered  with  a  watch  glass.     In  this  way  their  crystalline 
shape  is  preserved.     Yield,  80  per  cent  of  the  theory. 

Try  the  action  of  a  dilute  solution  of  sodium  hydroxide  on  a 
small  amount  of  the  oxime.     (?) 


NOTES 

1.  When  the  oxime  is  hydrolyzed  with  dilute  sulfuric  acid,  the 
angle  of  rotation  of  the  resulting  menthone  is  changed. 

2.  Like  most  terpene  compounds  menthone  oxime  is  somewhat 
volatile  and  therefore  should  not  be  left  in  the  open  or  in  a  vacuum 
desiccator  under  diminished  pressure  for  any  length  of  time. 


LABORATORY  EXPERIMENTS  101 


QUESTIONS 

1.  What  becomes  of  the  sodium  dichromate? 

2.  Write  the  general  structure  of  the  esters  of  chromic  acid. 

3.  Why  must  an  excess  of  sulphuric  acid  be  avoided? 

4.  Write  the  structures  of  menthone  oxime  and  of  hydroxyl- 

amine  hydrochloride. 

5.  In  hydroxylamine  hydrochloride  why  does  not  the  hydro- 

chloric acid  neutralize  the  OH-group? 

6.  What  is  the  purpose  of  the  90  per  cent  alcohol?    Why  not  use 

95  per  cent  alcohol? 

7.  Why  is  sodium  hydrogen  carbonate  used? 

8.  What  other  substances  could  be  used  in  place  of  the  sodium 

hydrogen  carbonate? 

9.  Is  it  necessary  to  use  the  hydrochloride '  of  hydroxylamine 

or    could    the    free   hydroxylamine    be    added    directly? 
Which  one  reacts? 

10.  How  can  an  aldehyde  or  a  ketone  be  regenerated  from  the 

oxime? 

11.  How  do  oximes  behave  towards  alkalies?    towards  boiling 

alcohol  and  sodium? 

12.  Show  how  oximes  can  be  used  in  organic  analytical  chemistry. 

13.  Give  an  experiment  which  will  show  that  menthone  is  a 

ketone  and  not  an  aldehyde. 

14.  How  can  you  prepare  menthol  from  menthone? 

15.  What  compound  is  formed  when  menthone  is  treated  with 

ethyl  magnesium  iodide  and  the  product  hydrolyzed? 

1 6.  Give  structure  and  name  of  acid  formed  by  treatment  of 

menthone  with  HCN  and  hydrolysis  of  the  cyanhydrin 
compound. 

17.  How  does  menthone  behave  toward  chlorine? 

18.  Give  the  structures  of  the  stero-isomeric  forms  of  menthone 

oxime. 


Experiment  No.  24 
FORMATION  OF  AN  ACID  CHLORIDE  FROM  THE  ACID 
Preparation  of  Acetyl  Chloride  from  Acetic  Acid 

The  apparatus  in  this  experiment  consists  of  a  60  cc.  distil- 
ling-flask, provided  with  a  dropping-funnel  (Fig.  6,  p.  36),  and 
attached  to  a  condenser.  A  second  distilling-flask  of  the  same 
capacity  tightly  connected  with  the  condenser  (if  a  good  cork 
connection  cannot  be  made,  use  a  piece  of  rubber  tubing  as  you 
would  a  bored  cork)  serves  as  the  receiver,  the  outlet  tube  being 
connected  to  a  calcium  chloride  tube.1  The  calcium  chloride 
in  the  tube  is  protected  at  each  end  with  a  plug  of  glass  wool  or 
cotton.  Since  the  receiving  flask  is  used  later  as  the  distilling- 
flask  without  transferring  the  distillate,  a  thermometer  and  well- 
fitting  cork  should  be  ready  before  the  operation  is  started. 
All  the  apparatus  must  be  perfectly  dry  and  the  connection  should 
be  so  made  that  the  product  does  not  come  in  contact  with  any 
cork  or  rubber.  Use  cork  stoppers  throughout,  except  as  noted 
above.  The  experiment  must  be  carried  out  under  a  hood,  or  the 
calcium  chloride  tube  connected  with  a  tube  opening  just 
above  the  surface  of  a  dilute  sodium  hydroxide  solution  contained 
in  a  bottle  and  the  fumes  then  led  into  the  draft  pipe.  The 
acetyl  chloride  fumes  in  the  air,  being  decomposed  by  moisture 
into  acetic  acid  and  hydrochloric  acid.  Care  must  be  exercised  in 
handling  both  reagents  and  product  to  keep  them  from  the  skin  and 
to  avoid  inhaling  the  vapors.  Acetyl  chloride  attacks  both  rubber 
and  cork;  therefore  the  apparatus  should  be  disconnected  as  soon 
as  the  experiment  is  completed,  and  the  product  should  be 

1  Be  careful  that  the  calcium  chloride  tube  does  not  become  stopped  up  dui 
ing  the  distillation. 

102 


LABORATORY  EXPERIMENTS  103 

kept  in  a  sealed  bottle 1  instead  of  the  ordinary  specimen 
bottle,  although  it  can  be  kept  for  a  few  days  in  a  glass- 
stoppered  bottle. 

Acetyl  chloride  has  a  high  vapor  pressure  and  therefore  good 
corks  must  be  used  and  the  joints  made  tight,  otherwise  serious 
losse?  wil]  occur.  It  is  best  to  plan  to  perform  the  experiment 
during  one  laboratory  period. 

Add  12  cc.  of  glacial  acetic  acid  to  the  distilling-fksk,  which 
is  immersed  in  cold  water  in  a  beaker.  Then  add  slowly  from  the 
dropping-funnel  7.5  cc.  of  phosphorus  trichloride.  When  all 
this  has  been  added,  mix  the  liquids  by  gently  shaking  the 
flask  and  allow  to  stand  for  about  one  hour.  Then  warm  the 
water  to  4o°-5o°  and  continue  the  heating  at  this  tempera- 
ture for  a  short  time.  The  liquid,  which  was  homogeneous  before 
heating,  finally  separates  into  two  layers;  the  upper  layer  consists 
mainly  of  the  acetyl  chloride,  and  the  lower  of  phosphorous 
acid.  Slowly  heat  the  water  to  boiling  until  nothing  further 
distills.  The  distillate  contained  in  the  same  distilling-flask, 
now  provided  with  the  thermometer,  is  carefully  redistilled. 
Collect  the  portion  that  distills  between  52°  and  55°  in  a  receiver 
protected  with  a  calcium  chloride  tube,  or  with  absorbent  cotton 
to  prevent  circulation  of  air. 

Acetyl  chloride  is  a  colorless  liquid  with  a  pungent  odor,  it 
fumes  in  contact  with  moist  air;  b.p.  53°,  sp.gr.  1.105  at  20°. 

After  the  yield  has  been  determined  perform  the  following 
test-tube  experiments: 

NOTE 

The  reactions  with  acetyl  chloride  are  usually  very  vigorous. 
Therefore,  when  carrying  out  experiments  with  it  care  should  be 
taken  that  the  test-tube  is  held  in  such  a  position  that  its  contents 
cannot  be  shot  out  into  the  face  of  the  experimenter  or  of  anyone  else. 

i.  Add  a  few  drops  of  acetyl  chloride  to  about  3  cc.  of  water 
in  a  test-tube.  The  acetyl  chloride  sinks  to  the  bottom  of  the 

1  A  thin-walled  bottle  of  soft  glass  with  an  extended  neck  which  can  be  sealed 
off  as  described  at  the  end  of  this  experiment. 


104          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

tube,  but  on  shaking  rapidly  dissolves,  and  heat  is  evolved. 
What  are  the  products? 

2.  To  about  i  cc.  of  ethyl  alcohol  add  i  cc.  of  acetyl  chloride 
drop  by  drop,  cooling  the  test-tube  under  the  tap.     Then  add 
an  equal  volume  of  water,  the  tube  being  cooled  as  before.     Make 
weakly  alkaline  with  sodium  carbonate  solution  and  add  common 
salt  until  no  more  dissolves.    What  is  the  pleasant-smelling 
substance  that  separates  out  as  a  mobile  layer  on  the  surface  of 
the  water  solution? 

3.  To  i  cc.  of  aniline  add  i  cc.  of  acetyl  chloride,  drop  by 
drop.    A  vigorous  reaction  occurs,  and  a  solid  separates.     Cool 
the  mixture  with  water  and  add  about  five  times  its  volume  of 
water.     What  substance  is  formed?    What  is  its  trade  name? 
Recrystallize  by  dissolving  it  in  hot  water  and  allowing  the 
solution  to  cool.     It  is  obtained  in  leaflets  which  melt  at  114° 
cor.    Determine   the  melting-point;   see  Expt.  12,  p.  58. 

Write  equations  for  all  the  above  reactions. 

Place  the  remainder  of  the  product  in  a  sealing  tube  or  bottle 
and  seal  off  the  neck  by  means  of  a  small,  blast-lamp  flame.    On 
account  of  the  volatility  of  the  acetyl  chloride  the  lower  part  of 
the  sealing  tube  must  be  kept  cool  by  means  of  a  cloth  saturated  j 
with  ice  water.     Total  yield,  12-14  grams. 

NOTE 

For  an  excellent  discussion  of  the  reaction  between  acetic  acid 
and  phosphorus  trichloride,  see  Brooks,  Journ.  Amer.  Chem.  Soc., 
34  (1912),  492-9- 

QUESTIONS 

1.  Write  the  equation  for  this  reaction. 

2.  When  is  PC15  used  to  replace  OH  groups  with  Cl? 

3.  What  is  the  product  remaining  in  the  first  flask? 

Is  the  second  equation  on  p.  142  in  Gattermann  correct? 

4.  Account  for  the  HC1  gas. 

5.  What  two  objections  are  there  to  the  use  of  PCls  in  certain 

cases? 

6.  Why  does  acetyl  chloride  fume  in  the  air? 


LABORATORY  EXPERIMENTS 


105 


7.  Compare  acetyl  chloride  and  benzoyl  chloride  with  regard 

to  their  stability  toward  water,  alkalies,  etc. 

8.  Compare  the  physical  characteristics  of  the  acyl  chlorides 

with  the  acid  from  which  they  are  derived. 

9.  How  can  the  following  classes  of  compounds  be  prepared 

from    acyl    chlorides:     esters,    amides,    acid   anhydrides, 
•~f^G  ke tones  and  *  3°-alcohols?  Apr*         <^^OffJ^."F'C. 

10.  How  is  acetyl  chloride  used  for  detecting  and  estimating 

OH  groups,  and  *  for  distinguishing  between  i°  or  2°  and 
3°  amines? 
*n.  What  is  the  Schotten-Baumann  reaction? 

12.  What  is  meant  by  acylation?     Acetylation? 

13.  What  other  reagents  are  used  for  acetylation? 

14.  How  can  acid  chlorides  be  distinguished  chemically  from 

alkyl  chlorides? 

*i5.  How  are  the  sulfone  chlorides  formed? 

*i6.  What  is  Hinsberg's  method  of  distinguishing  between  i°, 
2°  and  3°  amines?  (Bernthsen,  "Organische  Chemie,"  nth 
Ed.,  2d  par.,  p.  440;  Noyes,  "  Org.  Chem.  for  the  Lab.," 
2d  Ed.,  p.  160;  Clarke,  "  Org.  Anal,"  p.  36.) 

17.  What  is  sulfuryl  chloride  and  how  formed?     Thionyl  chlor- 

ide? 

1 8.  Compare   the   boiling-point   of   acetyl   chloride  with  that 

of  phosphorus  trichloride.      -7  ^ 

*  These  questions  are  not  required  for  study  in  the  "short"  course. 


C? 


^    ,1.  / 


p* 


3--.x  y 


<*l  K?tS 


7 


Experiment  No.  25 

FORMATION  or  AN  ESTER  FROM  THE  ALCOHOL  AND  THE  ACID 
Preparation  of  Ethyl  Acetate 

To  a  small  distilling-flask  connected  with  a  condenser  add 
a  mixture  of  10  cc.  of  absolute  ethyl  alcohol  and  12  cc.  of  cone, 
sulfuric  acid.  Insert  the  stem  of  a  dropping-funnel  into  the  neck 
of  the  flask  and  let  the  end  reach  below  the  surface  of  the  liquid. 
Heat  the  flask  in  an  oil-bath.1  When  the  temperature  of  the  oil 
reaches  145°  allow  a  mixture  of  15  cc.  of  absolute  alcohol  and 
15  cc.  of  (glaciaT)  acetic  acid  to  drop  slowly  into  the  liquid,  and 
as  soon  as  the  reaction  proceeds  regularly  add  the  mixture  at 
about  the  same  rate  at  which  the  products  distill.  Keep  the 
temperature  at  about  145°-! 50°  until  all  the  mixture  has  been 
added.  When  no  more  distills  over  treat  the  distillate  in  a  beaker 
vjwith  a  concentrated  solution  of  sodium  carbonate  until  there  is 
^no  further  effervescence  (?),  separate  the  layers  in  a  separatory 
funnel,  and  wash  the  upper  layer  with  about  its  own  volume  of 
saturated  salt  solution.  (?)  Separate  again,  dry  with  anhydrous 
sodium  sulfate  or  fused  potassium  carbonate,  and  distill.  Ethyl 
acetate  boils  at  77°,  its  specific  gravity  is  0.9239  at  o°,  and  it  is 
soluble  i  part  in  17  parts  of  water  at  17.5°.  Yield,  n  grams 
or  more.  £-^oU  Ht^  *S  ^°'c 

NOTE 

The  slower  the  distillation  in  the  first  reaction  the  better  the 
yield  will  be.  It  will  be  noticed  that  practically  nothing  distills  over 
until  the  temperature  has  almost  reached  145°. 

Hydrolysis  of  an  Ester 

In  a  small  flask  with  reflux  condenser  attached  heat  for  ten 
minutes  5  cc.  of  ethyl  acetate,  50  cc.  of  water,  and  2  grams  of 

1  A  shallow  iron  dish  and  rape-seed  oil  are  convenient  for  this  purpose.  For 
discussion  of  heating-baths,  see  foot-note,  p.  79. 

106 


LABORATORY  EXPERIMENTS  107 

sodium  hydroxide.  Then  distill  over  about  half  the  liquid. 
Test  the  distillate  for  alcohol  with  potassium  dichromate  (see 
Expt.  10,  "Reactions  of  Alcohols,"  p.  54).  Empty  the  remainder 
of  the  original  solution  into  a  porcelain  dish  and  evaporate  to 
dryness.  Dissolve  the  residue  in  water  and  acidify  with  sul- 
furic acid.  Note  the  odor.  (?) 

How  could  you  test  for  the  acid  by  a  chemical  method? 

Outline  a  procedure  for  preparing  a  derivative  of  the  alcohol  to 
confirm  your  qualitative  findings  (compare  methyl  ester  of  3.5- 
dinitrobenzoic  acid,  p.  55). 

QUESTIONS 

1.  Is  it  necessary  to  use  absolute  alcohol  in  the  preparation  L 

of  ethyl  acetate? 

2.  Could  hydrochloric  acid  be  used  in  place  of  cone,  sulfuric 

acid?  dilute  sulfuric  acid?     Explain. 

3.  What  would  be  the  effect  if  some  water  was  added  to  this 

reaction  mixture?  or  methyl  alcohol?  or  ethylene? 

4.  Would  any  ethyl  acetate  be  formed  without  the  presence  of 

sulfuric  acid?     If  any,  how  much  compared  to  the  yield 
when  sulfuric  acid  is  present? 

5.  What  is  the  object  of  keeping  the  temperature  between  145° 

and  150°?     What  happens  when  the  temperature  is  raised? 

6.  Would  it  make  any  difference  if  a  mixture  of  25  cc.  of  acetic 

acid  and  50  cc.  of  alcohol  was  run  into  the  reaction  flask 
instead  of  a  mixture  of  25  cc.  of  each? 

7.  Why  is  this  mixture  introduced  through  a  dropping-funnel,  , 

and  led  underneath  the  surface  of  the  solution? 

8.  Is  the  yield  of  ethyl  acetate  affected  in  any  way  by  dis-  ^, 

tilling  off  the  ethyl  acetate  as  it  is  being  formed? 

9.  Why  is  the  distillate  treated  with  sodium  carbonate?     Could 

sodium  hydroxide  solution  be  used  instead? 

10.  Why  is  the  ester  washed  with  salt  solution  instead  of  water? 

11.  Why  cannot  other  drying  agents,  such  as  calcium  chloride 

and  solid  potassium  hydroxide,  be  used  for  the  drying  of 
the  ethyl  acetate? 

12.  Solve  the  problems  on  p.  1 6 1,  in  Gattermann. 

13.  Point  out  all  the  conditions  that  are  used  to  give  a  maximum 

yield  of  the  ester. 

14.  What  would  you  expect  to  happen  when  methyl  acetate  is 

heated  with  dry  hydrogen  chloride?  with  an  alcoholic 
solution  of  hydrogen  chloride? 


Experiment  No.  26 
Hydrolysis  (Saponification)  of  Butter 

Dissolve  2  grams  of  sodium  hydroxide  in  2  cc.  of  water.  In  a 
porcelain  dish,  such  as  a  casserole  (not  a  glass  beaker.  Why?) 
heat  10  grams  of  butter  until  it  melts,  add  the  concentrated 
solution  of  sodium  hydroxide,  and  continue  the  heating  cautiously 
with  good  stirring  until  the  mixture  becomes  of  a  creamy  con- 
sistency. Pour  it  into  15  cc.  of  water  and  transfer  this  solution 
to  a  distilling-flask.  Acidify  with  20  cc.  of  dilute  sulfuric  acid 
(i  part  of  acid  to  4  of  water),  and  distill  over  about  15  cc. 

a.  Test  the  reaction  of  the  distillate  with  neutral  litmus.     (?) 

b.  To  what  is  the  odor  of  the  distillate  chiefly  due? 

c.  Of  what  does  the  oily  residue  in  the  flask  consist?    How 
could  you  prove  it? 

d.  Remove  the  oily  layer,  wash  it  several  times  with  water 
(?)  and  see  if  it  dissolves  in  dilute  sodium  hydroxide  solution. 
Add  a  drop  of  dilute  acetic  acid  to  the  solution  thus  made.     (?) 

e.  Test  a  small  portion  of  butter  for  unsaturated  radicals 
with  a  solution  of  bromine  in  carbon  tetrachloride. 

QUESTIONS 

1.  What  is  a  fat?  a  fatty  oil?  a  mineral  oil? 

2.  What  are  soaps  and  how  are  they  prepared? 

3.  In  your  experiment  what  solution  contained  the  soaps? 

4.  What  is  the  by-product  when  fats  are  saponified?     How  is  it 

purified? 

5.  What  is  rancid  butter?     Explain. 

*6.  What  is  meant  by  the  "  saponification  number  "? 
7.  What  advantage  has  an  alcoholic  solution  of  potassium  hy- 
droxide over  an  aqueous  solution  in  saponifying  fats? 

*8.  How  is  the  number  of  hydroxyl  groups  in  a  compound  deter- 
mined? 

*  Not  required  for  study  by  students  in  the  "short"  course. 
108 


LABORATORY  EXPERIMENTS  109 

9.  What  would  happen  if  "  nitroglycerine  "  was  boiled  with  an 
alcoholic  solution  of  potassium  hydroxide? 

10.  What  is  the  difference  in  the  behavior  of  the  two  esters, 

triolein  and  ethyl  bromide,  when  boiled  with  alcoholic 
potassium  hydroxide?  j 

11.  Can  acids  be  used  for  hydrolyzing  esters?     Compare  the 

rate  of  hydrolysis  with    alkali    and  with    acid  of  corre- 
sponding "  strengths." 

12.  What  is  the  irritating  gas  formed  when  a  fat  is  heated  alone? 

Explain. 

13.  What  are  the  products  formed  when  lecithin  is  saponified 

with  alkali?     (Compare  Expt.  27,  p.  no.) 

14.  What  is  a  wax?    What  difference  from  a  fat  is  noted  on 

saponifkation? 

15.  How  could  you  distinguish  in  the  laboratory  between  a  fatty 

oil  and  a  mineral  oil?  between  a  fat  and  a  wax? 


:.  of 


Experiment  No.  27 

ISOLATION  AND  STUDY  OF  A  NATURAL  PRODUCT 
Lecithin  from  Egg-yolk 

Grind  the  yolk  of  one  hard-boiled  egg  with  50  cc.  of  ether. 
Filter  and  wash  the  solid  material  twice  with  10  cc.  of  ether. 
Discard  the  solid  material.  Evaporate  the  combined  ether  ex- 
tracts and  washings  on  the  steam-bath.  Extract  this  residue 
twice  with  hot  alcohol,  using  10  cc.  each  time.  Pour  off  the 
alcohol  from  the  heavy  oil  through  a  small  filter.  Evaporate 
off  the  alcohol  from  the  alcoholic  filtrate,  dissolve  the  residue  in 
10  cc.  of  cold  ether,  and  add  20  cc.  of  acetone.  Stir  until  the 
particles  of  precipitated  lecithin  adhere  together  and  form  a 
ball.  Describe  its  properties. 

Boil  about  one-fourth  of  the  lecithin  with  about  10  cc. 
a  2N  solution  of  sodium  hydroxide.  Note  he  odor  of  the  gas 
evolved.  What  is  it?  Cool  the  solution.  Is  there  any  evidence 
of  the  formation  of  a  soap?  Filter,  dissolve  the  precipitate  in 
warm  water  and  add  dilute  hydrochloric  or  acetic  acid  to  the  solu- 
tion. What  is  precipitated? 

Test  a  part  of  the  lecithin  for  nitrogen  and  for  phosphorus 
(See  Expt.  28,  p.  112).  Results? 

REFERENCES 

MacLean,  "Lecithin  and  Allied  Substances,"  (1918)  (Longmans); 
Levene  and  West,  "Lecithin,  I. — Hydrolecithin  and  its  bearing  on  the 
constitution  of  cephalin,"  Journ.  Biol.  Chem.,  33  (1918),  111-7. 
Levene  and  West,  "Lecithin,  II. — Preparation  of  pure  lecithin; 
composition  and  stability  of  lecithin  cadmium  chloride."  Journ. 
Biol.  Chem.,  34  (1918),  175-86. 

110 


LABORATORY  EXPERIMENTS  111 

QUESTIONS 

1.  Write  the  structural  formula  of  lecithin. 

2.  Is  lecithin  a  name  for  a  single  substance  or  is  it  a  generic  term? 

Explain. 

3.  Why  is  the  first  extraction  residue  treated  with  hot  alcohol? 

4.  What  are  the  physical  properties  of  lecithin? 

5.  What  elements  did  you  find  present? 

What  other  methods  could  be  used  for  decomposing  the 
organic  matter  before  testing  for  phosphate? 

What  is  choline?  How  is  neurine  related  to  it?  Muscarine? 
Betaine? 


Experiment  No.  28 

Detection  of  Nitrogen,  Sulfur,  the  Halogens  and  Phosphorus 
in  an  Organic  Compound 

• 
Support  a  clean,  dry,  hard-glass  (Pyrex)  tube  (9  mm.  by.  100 

mm.)  in  a  clamp,  using  two  pieces  of  cork  about  5  mm.  thick 
for  protection,  or  pass  the  tube  through  a  hole  in  an  asbestos 
disc  in  such  a  way  that  the  tube  is  supported  by  the  flare  at  the 
top.  Prepare  a  small  piece  of  bright  metallic  sodium,1  not  more 
than  2  cmm.  and  drop  it  into  the  tube.  Apply  a  very  low 
blue  flame  (1.5  cm.  long)  now  and  then  until  the  sodium  melts 
and  there  is  a  layer  of  sodium  vapor  i  cm.  deep.  Drop  a  small 
amount  of  the  substance  to  be  tested  (diphenylthiourea, 
fe^S,  or  lecithin)  into  the  tube  from  the  point  of  a  knife 
lade,  anpl  continue  the  gentle  heating  while  the  decomposition 
^is  progressing,  being  careful  not  to  drive  the  vapors  of  the  sub- 
stance out  of  the  tube  by  too  strong  heating.  Finally  bring  the 
mass  to  red  heat  for  a  minute  and  then  allow  to  cool  to  room 
temperature. 

In  the  meantime  (for  the  sulfur  test)  prepare  about  2  cc.  of  a 
dilute  solution  of  ferrous  sulfate,  and  also  a  very  dilute  solution 
of  sodium  nitroprusside,  Na2(NO)Fe(CN)s,  by  adding  a  small 
crystal  to  2  cc.  of  water. 

To  the  cool  reaction-tube  add  two  or  three  drops  of  alcohol 
to  destroy  any  unused  sodium.  Use  a  stirring-rod  to  break  up 
the  charred  mass.  When  the  evolution  of  hydrogen  has  ceased 
cautiously  add  a  drop  or  two  of  water.  When  it  is  certain 
that  all  the  sodium  is  destroyed  add  more  water.  Filter  through 
a  small  wet  filter  paper  and  rinse  out  the  tube  with  three  or 
four  portions  of  water,  making  the  total  volume  used  about 
3  cc.  The  filtrate  should  be  water-white.  If  it  is  colored, 
the  decomposition  was  not  complete  and  should  be  repeated. 

1  Return  all  sodium  residues  to  the  bottle. 
112 


LABORATORY  EXPERIMENTS  113 

Make  alkaline  with  sodium  hydroxide  solution,  if  not  already 
so.     Divide  the  filtrate  into  three  portions. 

To  one  portion  in  a  test-tube  add  two  or  three  drops  of 
the  freshly  prepared  ferrous  sulfate  solution,  and  a. -very  small 
amount  of  potassium  fluoride.1  Stopper  the  tube  and  rotate 
the  contents  only  enough  to  mix  the  substance.  Allow  to  stand 
five  to  ten  minutes.  Then  acidify  with  dilute  sulfuric  acid 
(approx.  normal).  If  nitrogen  was  present  in  the  sample, 
a  precipitate  of  Prussian  blue  will  be  formed. 

NOTE 

Hydrochloric  acid  is  not  used  because  the  yellow  color  of  the 
ferric  chloride  and  the  blue  color  of  the  fine  precipitate  will  give  a 
green  color  at  the  end,  and  sometimes  no  blue  precipitate  is  formed. 

Dilute  two  or  three  drops  of  the  second  portion  of  the  filtrate 
to  2  cc.  and  add  a  drop  of  the  sodium  nitroprusside  solution. 
The  presence  of  sulfur  is  shown  by  the  appearance  of  a  violeTTor 
purplish-violet  color.  This  is  a  very  delicate  test  for  alkaline 
sulfides.  An  idea  of  the  amount  of  sulfur  present  may  be  gained 
by  acidifying  the  remainder  of  the  second  portion  of  the  original 
filtrate  with  acetic  acid  and  adding  a  solution  of  lead  acetate.  (?) 

To  the  third  portion  add  just  enough  dilute  hydrochloric  acid 
to  make  the  solution  react  acid,  and  then  add  two  or  three 
drops  of  ferric  chloride  solution.  If  a  blood-red  color  is  formed 
it  indicates  the  presence  of  a  thiocyanate.  However,  although 
nitrogen  and  sulfur  may  originally  be  present  in  the  sample, 
this  test  may  not  be  positive  because  the  sodium  thiocyanate 
first  formed  is  sometimes  decomposed  by  the  metallic  sodium 
into  sodium  sulfide  and  sodium  cyanide. 

REFERENCE 

Viehover  and  Johns,  "On  the  Determination  of  Small  Quantities 
of  Hydrogen  Cyanide,"  Journ.  Amer.  Chem.  Soc.,  37  (1915),  601-7. 

This  same  general  procedure  can  be  used  also  for  the  detec- 
tion of  other  elements  such  as  the  halogens  and  phosphorus. 

1  It  is  not  definitely  known  why  the  potassium  fluoride  is  more  efficient  in  aid- 
ing the  precipitation  of  the  Prussian  blue  than  any  other  salt.  Compare  Viehover 
and  Johns'  reference  above. 


114          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

For  the  halogens  the  fusion  is  carried  out  in  the  usual  manner 
and  the  water-white  filtrate  is  acidified  with  nitric  acid,  boiled 
(?)  and  treated  with  a  few  drops  of  silver  nitrate  solution.  If  it 
has  already  been  shown  that  nitrogen  and  sulfur  are  absent  it  is 
not  necessary  to  boil  the  solution  (?). 

For  phosphorus,  use  about  i  cc.  of  the  filtrate  from  the 
sodium  decomposition  in  the  nitrogen  test  and  boil  this  for  one 
minute  with  3  cc.  of  cone,  nitric  acid  (?).  Cool  the  solution  and 
add  twice  its  volume  of  ammonium  molybdate  reagent.  Heat 
the  tube  to  such  a  temperature  that  it  can  just  be  held  in  the  hand, 
then  set  aside.  If  phosphorus  was  present  in  the  original  sample 
a  yellow  crystalline  precipitate  of  ammonium  phospho-molybdate 
will  form. 

QUESTIONS 

1.  At  the  end  of  the  sodium  decomposition,  in  what  chemical 

combinations  are  the  nitrogen  and  the  sulfur  found? 

2.  How  does   the   alcohol   destroy   the   unattacked   sodium? 

Why  not  use  water  at  first? 

3.  Write  equations  for  the  reactions  involved  in  the  test  for 

nitrogen. 

4.  Why  is  the  mixture  acidified  with  sulfuric  acid  rather  than 

with  hydrochloric  acid? 

5.  How  else  may  sulfur  be  detected? 

6.  Explain  the  ferric  chloride  test. 

7.  Can  the  sodium  method  be  used  for  detecting  a  halogen: 

Suppose  a  halogen  and  nitrogen  are  both  present.     (?) 

8.  How  is  nitrogen  detected,  and  also  estimated,  by  the  soda 

lime  method? 

9.  In  what  combination  is  the  nitrogen  when  it  can  ordinarily 

be  detected  by  the  soda-lime  method? 

10.  What  is  the  Kjeldahl  method  for  the  estimation  of  nitrogen? 

11.  What  is  the  Dumas  or  absolute  method  for  the  estimation 
*        of  nitrogen? 


Experiment  No.  29 

FORMATION  OF  AN  ACID  AMIDE  FROM  THE  AMMONIUM  SALT  OF 

THE  ACID 

Preparation  of  Acetamide  from  Ammonium  Acetate 

The  ammonium  acetate  used  in  this  experiment  should  be 
>as  free  from  water  as  possible.  Press  out  the  material  on  a 
porous  tile  1  if  necessary. 

First  Method 

Under  a  reflux  condenser  heat  to  gentle  boiling  a  mixture 

of  15  grams  of  dry  ammonium  acetate  and  a  little  more  than  the 

I  same  amount  of  glacial  acetic  acid  for  three  to  four  hours.     Cool, 

j  transfer  the  liquid  to  a  6o-cc.  distilling-flask  connected  with  a 

I  water  condenser,  and  distill  until  the  temperature  reaches  160°. 

j  Discard  this  portion.     (Of  what  does  it  chiefly  consist?)     Replace 

the  water  condenser  by  a  small  distilling-flask,  allowing  the  outlet 

i  tube  of  the  first  one  to  pass  through  the  neck  of  the  second  one 

|  so  that  the  distillate  will  be  collected  in  the  bulb  of  the  second 

one.2     Continue  the  distillation  and  collect  the  portion  distilling 

above  160°.    Redistill  this  slowly  as  previously,  but  for  a  receiver 

;  attach  to  the  outlet  tube  of  the  distilling-flask  a  small  ordinary 

•  flask  or  large  test-tube,  which  has  been  weighed,  and  with  a  cork 

containing  a  channel  cut  in  the  side.     This  time  collect  the 

portion  distilling  2io°-2i5°.     The  product  solidifies  to  a  white 

crystalline  mass.     A  third  distillation  may  be  necessary  if  it 

.does  not  solidify  on  cooling.     Pure  acetamide  boils  at  222°  cor. 

Yield,  10  grams. 

1  For  use  of  porous  tile,  compare,  foot-note,  p.  56. 

2  It  is  not  usually  necessary  to  cool  the  receiving  flask.    If  this  is  done,  how- 
i  ever,  care  must  be  taken  not  to  allow  the  condensate  to  solidify  in  the  outlet  tube 

of  the  main  distilling-flask,  since  it  may  clog  it  and  cause  trouble. 

115 


116          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

The  peculiar  odor  characteristic  of  mice  excrement  in  the 
crude  substance  is  due  to  an  impurity  which  can  generally  be 
removed  by  re-crystallization.  Acetamide  is  deliquescent  and 
volatile  at  the  ordinary  temperature  and  pressure.  It  is  easily 
soluble  in  chloroform  and  in  alcohol,  and  difficultly  soluble  in 
ether. 

Recrystallization  of  Acetamide.  Determine  the  weight  of  the 
crude  product  by  weighing  the  receiver  again.  Add  some 
chloroform,  i  cc.  for  each  gram,  to  the  flask  or  tube,  attach  a 
reflux  condenser  and  heat  to  boiling  by  means  of  warm  water. 
Chloroform  boils  at  61°,  and  all  the  acetamide  will  be  dissolved 
within  a  few  minutes.  Disconnect,  and  pour  the  clear  hot 
solution  into  a  small  beaker  and  cover  with  a  watch  glass. 
Within  a  very  short  time  the  crystals  will  commence  to  form  and 
the  entire  mass  will  quickly  set  to  an  apparent  solid.  Note 
the  supercooling,  and  evolution  of  heat  when  crystallization 
begins.  (Explain.)  Cool  further  by  placing  the  beaker  in  cold 
water  or  ice.  Break  up  the  crystalline  mass  with  a  stirring-rod 
and  filter  rapidly  with  suction,  using  a  5  cm.  Buchner  funnel 
(Fig.  8,  p.  51),  or  the  method  for  suction  filtration  of  small 
quantities,  p.  56.  In  the  latter  case  use  a  6-7  cm.  funnel  and 
moisten  the  little  filter  paper  with  chloroform  before  turning  on 
the  pump.  Press  the  material  down  slightly  with  a  spatula  or 
glass  stopper.  On  account  of  the  very  hygroscopic  nature  of 
acetamide  the  filtration  must  not  be  prolonged,  otherwise  the 
substance  will  liquefy.  Yield,  80  per  cent  of  crude  product. 

1.  Heat    some    acetamide    with    dilute    sodium    hydroxide 
solution.     What  gas  is  evolved?    Acidify  with  dilute  sulfuric 
acid,  and  note  the  odor.     (?) 

2.  Heat  a  second  portion  of  acetamide  with  dilute  sulfuric 
acid.     Odor  of  vapors?    Neutralize  the  resulting  mixture  with 
dilute  sodium  hydroxide.     (?) 

NOTE 

Save  a  one-gram  sample  of  the  acetamide  for  the  methylamine 
experiment,  p.  120. 


LABORATORY  EXPERIMENTS  117 

Second  Method  (Sealed  Tube  Method) 

Put  1 5  grams  of  ammonium  acetate  into  an  ordinary  soft  glass 
"  bomb  "  tube,  packing  it  in  with  a  glass  rod  flattened  at  one 
end.  The  tube  should  not  be  more  than  half  full  when  sealed. 
Two  tubes  may  be  used  if  desired. 

Sealing  the  Bomb  Tubes.  The  open  end  of  the  tube  is  now 
sealed  in  the  blow-pipe  flame.  This  operation  requires  some 
care  and  a  little  skill.  It  is  advisable  to  practice  with  an  empty 
tube  first.  Grasp  the  tube  about  the  middle  with  the  left 
hand  and  while  it  is  inclined  at  an  angle  of  45°  heat  about  5  cm. 
of  the  tube  at  the  open  end  very  gradually  by  revolving  it 
for  several  minutes  in  a  small  smoky  flame.  Increase  the  size 
of  the  flame  slowly  until  it  is  large  enough  to  make  the  desired 
blue  flame  later  by  simply  turning  on  the  air  only.  Slowly  turn 
on  the  air  until  a  good  blast  flame,  about  10  cm.  in  length,  is 
obtained,  and  heat  the  end  of  the  tube  until  it  softens.  At  the 
same  time  heat  the  end  of  a  glass  rod,  about  12  cm.  long,  held  in 
ithe  right  hand,  and  seal  it  into  the  inside  of  the  tube.  Care 
'must  be  taken  to  make  a  good  seal — not  just  to  stick  it  on— 
j  otherwise  it  will  crack  off  when  the  tube  is  drawn  out.  Remem- 
iber  that  the  hottest  part  of  the  flame  is  at  the  end  of  the  inner 
j  blue  cone.  The  glass  is  allowed  to  cool  down  slowly  in  the  heat 
above  the  flame  with  the  rod  perfectly  in  line  with  the  tube,  and 
then  smoked.  Now  warm  the  tube  further  down  with  the  smoky 
I  flame,  low  at  first.  Gradually  make  the  flame  as  hot  as  possible 
and  about  7-10  cm.  long,  and  heat  the  tube  very  hot  around  a 
point  about  4  cm.  below  the  open  end  to  which  the  glass  rod 
jis  attached,  the  glass  rod  now  serving  as  a  support  while  the 
'tube  is  slowly  rotated.  The  glass,  evenly  heated,  begins  to 
'thicken  where  the  flame  plays  upon  it,  and  the  inside  diameter 
of  the  tube  contracts.  Rotate  it  carefully,  do  not  draw  it 
out,  and  keep  the  tube  in  line.  This  can  be  done  easily  if  the 
glass  rod  is  held  as  you  would  hold  a  pencil.  When  the  inside 
'diameter  of  the  tube  is  reduced  to  about  5  mm.  the  tube  is 
i removed  from  the  flame,  and  while  held  in  a  vertical  position  a 
Capillary  is  formed  by  very  slowly  drawing  out  the  thickened  part 


118         LABORATORY  MANUAL  OF  ORGANIC  CHEMISTYY 

of  the  tube,  and  holding  it  there  until  it  becomes  rigid.  It  is 
then  sealed  off  so  as  to  leave  a  capillary  about  4  cm.  long.  The 
capillary  is  necessary  as  will  be  seen  later  in  opening  the  tube. 
Smoke  the  sealed  end  and  allow  the  tube  to  stand  with  the  warm 
end  up  until  cold.  Then  remove  the  soot  with  filter  paper  or  a 
cloth.  The  instructor  must  pass  on  all  sealed  tubes  before  they 
are  heated  in  the  furnace. 

Heating  the  Tube.  Protect  the  eyes  with  goggles.  The 
sealed  tube  is  gently  put  into  an  iron  jacket  with  the  capillary 
at  the  open  end.  (See  instructor.)  Place  it  in  the  bomb 
furnace  so  that  the  open  end  of  the  jacket  is  towards  the  wall. 
Slide  in  the  guard,  see  that  the  end  of  the  furnace  near  the  wall 
is  raised  and  properly  fastened,  and  then  place  a  thermometer 
in  the  top  of  the  furnace.  Gradually,  thirty  to  forty  minutes, 
raise  the  temperature  up  to  2oo°-2io°,  at  which  temperature 
the  bomb  is  heated  for  three  hours.  Do  not  allow  the  tempera- 
ture to  go  higher  because  an  explosion  will  result.  The  tem- 
perature should  be  noted  about  every  thirty  minutes.  The 
heating  can  be  interrupted  at  any  time. 

Opening  the  Sealed  Tubes.  The  tubes  are  always  allowed 
to  cool  overnight.  No  one  should  enter  the  cannon  room  without 
wearing  goggles  to  protect  the  eyes.  In  no  case  whatsoever  should 
a  sealed  tube  be  taken  out  of  the  iron  casing  for  examination  or  for 
any  other  purpose.  When  being  opened  the  tube  is  held  in  such  a 
position  that  neither  the  operator  nor  anyone  else  can  be  injured  in 
case  of  bursting.  The  tube  should  be  opened  in  the  cannon  room. 
It  should  never  be  taken  out  into  the  laboratory  unopened. 

The  contents  of  the  tube  are  now  liquid.  The  protecting 
case  of  iron,  containing  the  tube,  is  removed  from  the  furnace 
and  held  in  a  slightly  inclined  position,  the  end  of  the  capillary 
being  higher  than  the  rear  end.  By  means  of  a  slight  jerk  the 
capillary  of  the  glass  tube  is  caused  to  project  from  the  jacket. 
The  extreme  end  of  the  capillary  is  now  held  in  the  flame  of  a 
Bunsen  burner.  If  there  is  any  internal  pressure  in  the  tube, 
the  glass  on  becoming  soft  will  be  blown  out  and  the  gases  will 
escape  from  the  opening  thus  made.  Should  no  gas  be  released 
even  at  red  heat  (which  sometimes  is  the  case  in  this  experiment) 


LABORATORY  EXPERIMENTS  119 

the  end  may  be  broken  off  by  a  sharp  blow  with  a  file.  The  glass 
tube  is  now  taken  out  of  the  iron  jacket.  A  deep  file  mark  is 
made  in  the  wide  part  of  the  tube  about  an  inch  below  the 
"  shoulder,"  and  this  is  touched  lightly  with  the  hot  end  of  a 
glass  rod  previously  heated  to  fusion  in  the  blast  flame.  If 
the  crack  caused  by  this  does  not  extend  entirely  around  the 
tube,  the  extreme  end  of  it  is  extended  by  applying  the  hot  end 
of  the  glass  rod  again  so  that  the  conical  end  may  be  lifted  off. 
Purify  the  product  as  in  the  first  method  above. 

QUESTIONS 

1 .  Why  must  the  ammonium  acetate  be  dry? 

2.  Explain  why  the  acetic  acid  is  used  in  the  first  method. 

3.  By  means  of  structural  formulas  indicate  the  "steps"  in  the 

hydrolysis  of  a  cyanide. 

4.  How  can  acetamide  be  prepared  from  methyl  cyanide? 

5.  What  is  the  action  of  phosphorus  pentoxide  on  acetamide? 

6.  What  other  methods  are  used  for  forming  amides? 

7.  How  are  the  substituted  amides  prepared?    E.g.,  acetanilide. 

8.  What  are  the  chemical  properties  of  the  amides  as  shown  by 

their  behavior  toward  (i)  dry  HC1  hi  ether,  (2)  bromine, 
(3)  bromine  and  potassium  hydroxide,  "(4)  mercuric 
oxide,  (5)  nitrous  acid,  *(6)  PC15,  (7)  aq.  HC1?  (8) 
aq.  KOH? 

*g.  What  is  an  imide?    How  formed?    Ex.  succinimide. 

;io.  What  is  the  action  of  ale.  KOH  on  an  imide?  What  use  is 
made  of  this  reaction? 

ii.  Look  up  the  structure  of  urea  and  show  how  it  is  related 
to  the  amides.  What  is  its  chemical  name? 

*  These  questions  are  not  required  for  study  in  the  "short"  course. 


Experiment  No.  30 

FORMATION  AND  STUDY  or  A  PRIMARY  AMINE 
Methyl-amine  from  Acetamide 

In  a  60  cc.  distilling-flask  dissolve  2.5  grams  of  sodium 
hydroxide  in  6  cc.  of  distilled  water  (ammonia  free).  Cool, 
and  then  (under  the  hood)  cautiously  add  through  a  funnel 
i  cc.  of  bromine  (not  bromine  water).  Shake  and  cool.  Now 
add  i  gram  of  acetamide,  stopper  with  a  cork,  slant  the  flask  a 
little  and  allow  the  end  of  the  outlet  tube  to  dip  just  below  the 
surface  of  6  cc.  of  distilled  water  (ammonia  free)  contained  in  an 
open  test-tube.  Heat  carefully  with  a  small,  moving  flame  1 
until  the  mixture  becomes  clear  and  vapors  are  vigorously 
evolved;  then  remove  the  flame,  but  resume  the  heating  and  con- 
tinue for  several  minutes  after  the  main  reaction  has  subsided. 
If  the  water  in  the  receiver  begins  to  run  back  remove  the 
stopper  temporarily. 

1.  Note  the  odor.     Is  it  exactly  like  that  of  ammonia? 

2.  Test  the  reaction  of  the  solution  with  neutral  litmus.  (?) 

3.  Add  a  drop  of  the  solution  to  i  cc.  of  a  very  dilute  solution 
of  ferric  chloride.  (?)     Repeat  with  dilute  ammonium  hydroxide 
instead  of  the  amine  solution.  (?)     Compare. 

4.  Add  a  drop  of  the  solution  to  i  cc.  of  a  very  dilute  solution 
of   cupric   sulfate.     If   the  precipitate   first   formed   does   not 
dissolve  add  another  drop  of  the  solution.   (?)     Repeat,  using 
dilute  ammonium  hydroxide.     (?)     To  what  is  the  color  in  each 
instance  due? 

5.  To  the  remainder  of  the  solution  in  an  evaporating  dish 
add  cone,  hydrochloric  acid  drop  by  drop  with  stirring  until 

1  Strongly  alkaline  solutions  bump  considerably. 
120 


LABORATORY  EXPERIMENTS  121 

the  solution  reacts  acid  to  litmus.  What  are  the  fumes?  Evapo- 
rate to  dryness  on  the  water-bath.  What  is  the  white  residue? 
Transfer  the  residue,1  which  is  hygroscopic,  to  a  test-tube  and 
add  a  small  amount  of  sodium  hydroxide  solution.  Boil  gently. 
Again  note  the  odor  of  the  vapors.  Hold  a  stopper  moistened 
with  cone,  hydrochloric  acid  near  the  mouth  of  the  tube.  (?) 
Test  the  inflammability  of  the  gas. 

6.  Add  a  drop  of  silver  nitrate  solution  to  a  very  dilute 
solution  of  ethyl  ammonium  chloride  (ethylamine  hydrochloride). 
Explain  your  result. 

QUESTIONS 

1.  Explain  the  formation  of  methyl  amine  from  acetamide. 

2.  Why  should  you  expect  methyl  amine  to  give  an  alkaline 

reaction  in  aqueous  solution? 

3.  Is  methyl  ammonium  hydroxide  a  "  stronger  "  base  than 

ammonium  hydroxide?     Explain. 

4.  Write  the  equations  for  the  reaction  with  ferric  chloride 

and  with  cupric  sulfate. 

5.  How  does  methyl  amine  react  with  hydrochloric  acid?    the 

product  with  sodium  hydroxide? 

6.  Compare   the  reaction  of  ethyl   ammonium   chloride   and 

ethyl  chloride  with  silver  nitrate.     How  can  you  account 
for  the  difference? 

7.  What  is  the  carbyl  amine  (isonitrile)  test  for  i°  amines? 

8.  How  can  you  distinguish  between  i°,  2°,  and  3°  amines? 

9.  What  compounds  are  formed  by  the  treatment  of  amines  with 

chlorplatinic   acid?     How   can   these   salts   be   used   for 
determining  the  molecular  weights  of  the  bases? 

10.  Compare  the  action  of  bromine  and  sodium  hydroxide  on 

urea  with  the  action  of  this  same  reagent  on  acetamide. 

11.  What  practical  use  is  made  of  the  reaction  in  No.  10? 

1  Save  a  few  crystals  of  the  hydrochloride  for  making  methyl  mustard  oil, 
p.  123. 


Experiment  No.  31 
Ethyl  Isocyanate 

Grind  together  equal  parts  (about  0.5  gram)  of  dry  potassium 
or  sodium  cyanate  l  and  dry  potassium  ethyl  sulfate.  Place  the 
mixture  in  a  dry  test-tube  and  heat  carefully.  A  liquid  soon 
begins  to  distill  and  partially  condenses  on  the  walls  of  the 
test-tube.  Note  its  odor.  (Care!) 

1.  What  is  its  structural  formula? 

2.  Why  must  the  reacting  substances  be  dry?     Explain  fully. 

3.  What  happens  when  the  liquid  obtained  above  is  boiled 

with  water? 

4.  How  do   the  isocyanates  react  with   alcohol?     Show  how 

this  reaction  can  be  used  in  the  identification  of  alcohols: 
also  amines. 

5.  Give  the  reasons  for  assigning  the  accepted  structural  formula 

for  the  isocyanates. 

6.  Do  esters  of  cyanic  acid  itself  exist?     Can  you  give  any  reason? 

1  Not  cyanide. 


122 


Experiment  No.  32 
Methyl.  Mustard  Oil  (Methyl  Isothiocyanate) 

In  a  test-tube  mix  a  few  crystals  of  methyl  amine  hydro- 
chloride  (Expt.  30,  test  5,  p.  120),  one  drop  of  carbon  bisulfide, 
and  one  or  two  drops  of  a  strong  solution  of  sodium  hydroxide. 
After  a  few  seconds  add  a  little  water  and  slightly  more  than 
enough  silver  nitrate  solution  (N/io)  to  react  with  the  potassium 
hydroxide.  (?)  Bring  to  a  boil.  The  odor  of  the  mustard  oil 
will  at  once  become  pronounced. 

1.  Outline  all  the  "  steps  "  in  this  reaction. 

2.  Do  all  amines  (i°,  2°,  3°)  give  this  reaction?    Therefore, 

what  use  can  be  made  of  the  reaction? 

3.  How  can  you  distinguish  chemically  between  an  isocyanate 

and  a  thiocyanate? 

4.  Which  compound  of  this  series  is  found  in  true  mustard  oil? 

Does  the  name  of  its  hydrocarbon  radical  have  any  sig- 
nificance in  organic  nomenclature? 


123 


Experiment  No.  33 

HYDROLYTIC    PREPARATION,    SEPARATION    AND    PURIFICATION 
OF  AN  AMINO  ACID 

Preparation  of  Glycocoll  (Glycine)  from  Hippuric  Acid 

Heat  to  slow  boiling  i  gram  of  hippuric  acid  and  15  cc.  of 
cone,  hydrochloric  acid  in  a  250  cc.  flask  under  reflux  condenser 
for  thirty  minutes.  During  this  time  have  a  tube  connected 
with  the  top  of  the  condenser  to  lead  the  fumes  into  a  flask  con- 
taining dilute  sodium  hydroxide  solution.  The  opening  should 
be  above  the  surface  of  the  alkaline  liquid  and  the  flask  should  be 
loosely  stoppered  with  cotton.  Toward  the  end  of  the  hydrol- 
ysis crystals  (?)  are  deposited  on  the  inside  walls  of  the  con- 
denser. 

After  the  thirty  minutes'  heating  disconnect  the  apparatus, 
add  10  cc.  of  water  to  the  main  reaction  mixture  and  cool  with 
running  water.  Filter  off  the  crystals  with  suction  and  save 
both  the  precipitate  and  the  filtrate.  Dry  the  white  crystalline 
product  and  determine  its  melting-point.  Test  its  solubility 
in  ether.  Dissolve  out  the  deposit  in  the  condenser  with  ether, 
evaporate  the  ether,  and  determine  the  melting-point  of  the 
residue.  Compare  with  that  obtained  from  the  hydrochloric 
acid  solution. 

Evaporate  the  filtrate  to  dry  ness  on  the  water-bath.  Add 
15  cc.  of  water  and  filter  off  any  insoluble  matter.  Neutralize 
exactly  with  dilute  sodium  hydroxide  solution,  using  litmus 
paper  for  the  tests.  Filter  again,  if  necessary.  Add  about 
0.5  gram  of  basic  copper  carbonate  and  warm  with  stirring.  A 
deep  blue  color  is  obtained,  which  is  characteristic  of  the  solu- 
tions of  the  copper  salt  complexes  of  many  of  the  monamino 
acids.  Filter  the  solution  while  still  hot  and  allow  the  filtrate 

124 


LABORATORY  EXPERIMENTS  125 

to  cool.  Separate  the  blue  needles  of  the  copper  salt  complex 
which  have  been  formed,  and  concentrate  the  nitrate  to  obtain 
a  second  portion.  Dissolve  the  combined  product  in  20  cc.  of 
warm  water,  saturate  the  warm  solution  with  hydrogen  sulfide 
gas  (which  has  been  washed  with  water),  filter  and  carefully 
evaporate  to  dryness  at  a  low  temperature,  4o°-5o°,  or  allow  to 
evaporate  at  room  temperature.  Complete  the  drying  on  the 
steam-bath.  Extract  the  residue  with  a  little  water  and  filter 
off  any  copper  sulfide  with  suction.  Sometimes  gravity  filtra- 
tion and  the  use  of  a  very  small  wet  filter  paper  is  better,  espe- 
cially for  a  second  filtration.  The  filtrate  should  be  water 
white.1  Concentrate  the  clear  colorless  solution  to  a  small  vol- 
ume and  allow  to  crystallize  in  a  small  round-bottomed  crystal- 
lizing dish.  Beautiful  crystals  can  be  obtained  in  this  way. 
Otherwise,  when  the  volume  of  the  solution  is  about  i  cc.  or 
less,  pour  it  into  3-4  cc.  of  alcohol  with  stirring.  White  needles 
will  be  precipitated.  Set  aside  for  complete  precipitation,  and 
filter  before  all  the  mother  liquor  has  evaporated.  (Why?) 
Dry  and  determine  the  melting-point  of  the  pure  white  amino 
acid  thus  obtained.  (?)  What  is  the  chemical  name  of  this  com- 
pound? Hand  in  the  product  and  put  the  melting-point  which 
you  have  found  upon  the  label. 

NOTE 

The  above  experiment  is  a  sort  of  "index"  of  your  experimental 
skill.  Only  by  very  careful  manipulation  can  the  small  amount  of 
pure  product  be  obtained. 

1  Sometimes  considerable  difficulty  is  experienced  in  removing  all  the  copper 
sulfide  and  in  getting  the  solution  colorless.  Apparently  the  copper  sulfide  forms 
a  soluble  complex  with  the  amino-acid,  or  is  peptized  by  the  excess  of  hydrogen 
sulfide  and  becomes  colloidal.  Similar  difficulties  are  found  in  removing  mer- 
curic sulfide  from  organic  solutions.  Warming  with  a  good  decolorizing  carbon 
helps  to  remove  both  the  copper  sulfide  and  any  color.  If  it  is  due  to  colloidal 
cupric  sulfide  then  an  excess  of  hydrogen  sulfide  should  be  avoided.  An  electro- 
lyte cannot  be  added  to  precipitate  the  colloidal  material  since  it  will  contaminate 
the  product,  although  a  trace  of  an  aluminium  salt  (which  contains  a  trivalent 
ion)  would  be  helpful  if  properly  used.  If  the  solution  is  heated  too  much  the 
color  is  deepened  and  it  is  not  easy  to  get  rid  of  it.  It  is  known,  however,  that 
you  can  evaporate  a  solution  of  pure  glycocoll  almost  to  dryness  over  a  free  flame 
without  producing  any  color;  in  fact,  no  color  is  developed  even  if  a  little  sulfurig 
acid  is  present. 


I 


126          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 


QUESTIONS 

1.  What  is  the  structure  of  hippuric  acid?    Point  out  its 

chemical  groupings. 

2.  In  the  hydrolysis  of  hippuric  acid  what  compounds  are 

formed?    Write  their  structures. 

3.  Of  what  does  the  deposit  in  the  condenser  consist? 

4.  Why  is  the  reaction  mixture  diluted? 

5.  Why  is  the  filtrate  evaporated  to  dry  ness? 

6.  What  is  left  after  the  evaporation  to  dryness? 

7.  Write  the  reaction  for  the  neutralization.     (See  also  ques- 

tion No.  n.) 

8.  Why  not  use  copper  sulfate  for  preparing  the  copper  salt? 

Could  it  be  used  at  all? 

9.  What  advantage  has  a  round-bottomed  crystallizing  dish 

over  a  flat-bottomed  one. 

10.  Discuss  the  structure  of  amino-acetic  acid  (glycocoll,  glycine) . 

Account  for  its  high  melting-point. 

11.  How  are  amino  acids  estimated? 

12.  Give   three   methods   of   forming   glycocoll,    including   its 

preparation,  for  example,  from  gelatine. 

13.  How  can  you  prepare  hippuric  acid? 

14.  What  is  glycyl-glycine?    Its  preparation  by  two  different 

methods? 

15.  Compare  the  structure  of  hippuric  acid  with  that  of  a 

dipeptide. 

1 6.  How  are  polypep tides  prepared? 

17.  How  are  the  amino  acids  separated  and  identified  in  the 

mixture  obtained  by  the  hydrolysis  of  a  protein? 

18.  Give  names  and  structures  of  the  important  amino  acids. 


Experiment  No.  34 
Hydrolysis  of  Cane  Sugar  and  Preparation  of  Phenylglucosazone 

Dissolve  2  grams  of  cane  sugar  in  20  cc.  of  water.     Test  a 
few  drops  of  this  solution  with  Fehling's  solution  (mix  5  cc.  of 
each  part,  boil,  and  then  add  the  solution  to  be  tested),  and 
also  test  with  ammoniacal  silver  nitrate.     Result?    Add  0.5  cc. 
of  cone,  hydrochloric  acid  to  the  main  solution,  and  place  the 
tube  in  water  kept  at  70°  for  five  minutes.     Cool  under  running 
water.     Exactly    neutralize    2-3    cc.    with    dilute    ammonium 
i  hydroxide  solution,  and  then  test  again  with  Fehling's  solution 
!  and  also  with  the  ammoniacal  silver  nitrate.     (?)     If  a  light 
I  colored  precipitate  is  obtained  with  the  silver  solution  add  more 
j  ammonium  hydroxide  until  it  dissolves.     (?)     Explain  all  re- 
1  suits. 

Neutralize  with  ammonium  hydroxide  10  cc.  of  the  hydro- 
lyzed  sugar  solution,  make  up  to  20  cc.  with  water,  place  the  solu- 
I  tion  in  a  large  test-tube  (No.  3),  and  add  2  cc.  of  phenylhydra- 
zine 1   and  3  -cc.   of  glacial  acetic  acid.     Mix  well.     Stopper 
loosely  with  a  cork  to  prevent  evaporation,  and  set  the  tube  into 
\. water  which  has  been  brought  to  boiling2  and  let  stand  for 
one-half  hour.     Masses  of  fine  yellow  crystals  of   the  osazone 
soon  settle  out.     Cool,  filter  off  the  osazone  in  a  Buchner  funnel, 
and  wash  with  cold  water.     Recrystallize  as  follows:   Place  the 
yellow  product  in  a  250  cc.  Erlenmeyer  flask  and  add  a  mixture 
of  1 20  cc.  of  alcohol  and  60  cc.  of  water,  attach  an  upright  con- 
denser or  cover  with  a  small  watch  glass,  set  the  flask  on  the  steam- 
.  bath  and  heat  until  all  or  practically  all  the  substance  is  dissolved. 

1  Phenylhydrazine  is  poisonous.     Its  vapors  should  not  be  breathed,  and  it 
should  not  be  allowed  to  come  into  contact  with  the  skin  since  it  produces  an 

;  intolerable  itching.    Dilute  acetic  acid  will  remove  phenylhydrazine. 

2  Do  not  heat  after  placing  the  tube  into  the  bath,  otherwise  a  dark  product 
will  be  obtained. 

127 


128 


LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 


In  order  to  prevent  crystallization  in  the  filter,  the  solution 
should  be  filtered1  at  once  through  a  fluted  filter  in  a  glass  funnel 
set  in  a  hot-water  funnel,  using  a  stirring  rod  to  direct  the  flow  of 
the  hot  solution  into  the  filter.  The  hot- water  funnel  consists  of  a 
double-walled  copper  jacket  for  an  ordinary  funnel,  with  a  side 
tube  for  heating  the  water  within  (Fig.  12).  Steam  may 
be  passed  into  it  instead  of  using  water.  If  a  burner  is  used, 
it  must  be  removed  when  you  are  filtering  inflammable  liquids, 


HOT  WATER 


FIG.  12. 

as  in  this  case.     The  stem  of  the  glass  funnel  should  not  project 
more  than  2-3   cm.  below  the  neck  of  the  hot-water  funnel. 

1  A  fluted  filter  is  made  by  first  folding  a  large  circular  filter  paper  in  the  ordi- 
nary way.  Then  half  open  it,  and  bring  one  corner  in  to  the  center  of  the  hemi- 
circle  and  crease  the  paper.  Bring  back  this  same  corner  to  the  edge  of  the  fold 
just  made,  and  crease  again.  Now  fold  this  back  to  the  middle  line  of  the  original 
hemicircle.  Repeat  with  the  other  quadrant.  This  gives  an  alternating  series  of 
folds.  When  completely  opened,  it  will  be  noticed  that  there  are  two  places  where 
the  paper  would  lie  flat  against  the  walls  of  the  funnel.  Fold  each  one  of  these  in  a 
half  fold  to  make  them  similar  to  the  others.  A  fluted  filter  gives  very  rapid 
filtration.  (Why?) 


LABORATORY  EXPERIMENTS  129 

(Why?)  The  osazone  almost  immediately  begins  to  crystallize 
out  of  the  filtrate.  Filter,  when  cold,  with  suction,  and  set  aside 
the  product  to  dry  on  a  porous  plate  covered  with  a  watch 
jlass.  Determine  the  melting-point.  Pure  phenylglucosazone 
is  a  bright  yellow  finely  crystalline  substance  which  melts  at 
205°-2o6°  uncor.;  or  208°  cor.,  when  the  rate  of  heating  is 
0  in  two  to  three  seconds.1 

The  osazone  should  be  prepared  and  recrystallized  during 
one  laboratory  period.  Yield,  about  1.2  grams. 

NOTES 

1.  Solubility  of  phenylglucosazone: 

o.oi  part  dissolves  in  100  parts  of  boiling  water. 
0.0042  part  dissolves  in  100  parts  of  water  at  20°. 
0.031  part  dissolves  in  100  parts  of  5%  acetic  acid  at  20°. 

2.  If   the  phenylhydrazine   is   not  available,   use   instead   of  it 
and  the  acetic  acid,  2  grams  of  phenylhydrazine  hydrochloride  and 
3  grams  of  crystalline  sodium  acetate.    Explain. 

Phenylhydrazine  hydrochloride  when  pure  is  a  white  crystalline 
substance,  but  when  moist  or  impure  it  rapidly  decomposes  and 
darkens  on  keeping.  Unless  the  pure  white  substance  is  used  dark 
tarry  spots  will  be  found  in  the  reaction  mixture.  These  will  be 
removed  in  the  recrystallization  unless  there  is  a  large  amount. 

In  connection  with  the  identification  of  sugars  by  means  of  the 
rate  at  which  the  osazone  begins  to  precipitate,  Mulliken  describes 
the  method  of  obtaining  pure  phenylhydrazine  hydrochloride  from 
phenylhydrazine,  "Identification  of  Pure  Organic  Compounds," 
Vol.  I,  foot-note,  p.  32. 

In  order  to  prevent  the  decomposition  Boeseken  advises  using 
the  sulfite  salt  instead  of  the  hydrochloride,  Chem.  Weekblad,  7, 
•934;  Chem.  Abs.,  5  (1911),  2078. 

3.  Phenylglucosazone  is  also  known  as  phenylfructosazone,  and 
also  as  phenylmannosazone.     (Why?) 

1Garard  and  Sherman:  Journ.  Amer.  Chem.  Soc.,  40  (1918),  957,  and  com- 
pare, p.  58  of  melting-point  experiment. 


130          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 


QUESTIONS 

1.  Why  would  you  expect  cane  sugar  to  be  soluble  in  water? 

2.  What  are  the  two  mono-saccharides  in  invert  sugar? 

3.  Write  the  structural  formulas  for  cane  sugar  and  the  sub- 

stances in  invert  sugar. 

4.  Show  by  means  of  its  structure  that  cane  sugar  is  an  ace  tale. 

5.  What  does  the  behavior  of  cane  sugar  toward  Fehling's 

solution  and  ammoniacal  silver  nitrate  solution  indicate 
in  its  structure? 

6.  Why  is  the  invert  sugar  solution  neutralized  with  ammonium 

hydroxide  solution  before  it  is  tested  with  Fehling's 
solution? 

7.  What  is   the   white   precipitate   formed   when   insufficient 

ammonium  hydroxide  is  used  in  the  silver  mirror  test? 

8.  Explain  why  the  same   concentration   of   acetic  acid  as  of 

hydrochloric  acid  in  water  would  not  hydrolyze  cane  sugar 
as  rapidly. 

9.  How  can  you  show  that  cane  sugar  is  an  alcohol? 

10.  Explain  why  it  is  that  invert  sugar  can  be  oxidized  by 

Fehling's  solution  although  the  larger  portion  of  the 
mono-saccharides  in  it  are  known  to  be  in  the  lactone; 
form. 

11.  Explain  how  the  reaction  between  Fehling's  solution  and 

invert  sugar  can  be  used  as  a  quantitative  method  for  the, 
estimation  of  cane  sugar  in  the  presence  of  known  amounts  i 
of  glucose. 

12.  Explain  why  invert  sugar  yields  only  one  osazone. 

13.  For  what  purpose  is  acetic  acid  added  in  the  formation  of 

the  glucosazone  from  the  hydrolyzed  cane  sugar? 

14.  Could  strong  hydrochloric   acid  be  used  in  place  of  the 

glacial  acetic  acid  in  the  formation  of  the  osazone? 

15.  Can  invert  sugar  form  hydrazones  and  if  so  what  would  be 

their  chemical  structure? 

16.  Explain  how  the  hydrazones  and  osazones  are  of  value  to 

the  analyst  in  identifying  sugars? 
*i7.  Could  any  other  hydrazines  besides  phenyl  hydrazine  be 

used  for  the  purpose?    Are  they  ever  used,  and  why? 
*i8.  Can  you  give  any  reason  why  the  hydrazones  of  glucose  and 

mannose  should  be  different  in  physical  properties  since  the 

two  mono-saccharides  differ  only  in  a  sterochemical  way? 
*ig.  What  is  formed  when  the  osazone  is  heated  with  cone. 

hydrochloric  acid? 


LABORATORY  EXPERIMENTS  131 

'20.  How  can  d-glucose  be  transformed  into  ^-fructose?  into 

d-mannose? 
''2i.  How  can  d-fructose  be  transformed  into  (/-glucose? 

22.  What  is  a-methyl  glucoside?     How  prepared? 

23.  Of  what  does  the  Benedict-Fehling  solution  consist?     What 

advantage  has  it  over  the  Fehling  solution  in  the  test 
for  glucose  in  a  physiological  solution  like  urine?  (Hawk, 
"  Practical  Physiological  Chemistry,"  5th  Ed.  (1916), 
27, 417-8;  Plimmer,  "  Practical  Organic  and  Bio-chemistry 
(1915),  191.) 

*  These  questions  are  not  required  for  study  in  the  "short"  course. 


Experiment  No.  35 
Pentoses  (Furfural  Test) 

A  solution  of  a  pentose  is  first  made  by  the  acid  hydrolysis 
of  a  pentosan  such  as  gum  arabic  or  an  ordinary  corn  cob,  and 
then  the  presence  of  the  pentose  is  shown  by  the  colored  com- 
pound formed  by  the  action  of  the  decomposition  product  of  the 
pentose  with  hydrochloric  acid  and  aniline  acetate. 

Make  up  30  cc.  of  a  solution  of  dilute  hydrochloric  acid  (sp.gr. 
i. 06)  by  mixing  9  cc.  of  cone,  hydrochloric  acid  and  21  cc.  of 
water.  Pour  10  cc.  of  this  dilute  acid  into  a  100  cc.  flask  and  add 
about  0.2  gram  of  gum  arabic.  Slowly  bring  to  a  boil  over  a 
low  flame  and  boil  gently  for  five  to  ten  minutes.  Withdraw 
the  flame,  and  while  the  vapors  are  coming  out  place  in  the  mouth 
of  the  flask  a  roll  of  filter  paper  which  has  been  soaked  in  a 
solution  of  aniline  acetate,  and  from  which  the  excess  of  the 
solution  has  been  removed  by  pressing  between  filter  papers, 
The  test  should  be  made  while  the  paper  is  still  moist.  The 
aniline  acetate  solution  is  prepared  by  mixing  2  cc.  each  of 
aniline,  glacial  acetic  acid  and  water.  A  bright  crimson  color 
on  the  aniline  acetate  paper  indicates  the  presence  of  furfural 
from  the  action  of  the  hydrochloric  acid  on  the  pentose. 

Repeat  the  above  experiment,  using  0.2  gram  of  ground 
corn  cob. 

Some  of  the  hexoses  also  give  a  pink  color  in  this  same  test, 
but  the  color  generally  is  not  so  pronounced.  Repeat  the 
experiment,  using  the  same  amount  of  cane  sugar,  and  compare 
the  color  produced  with  that  from  the  pentoses. 

REFERENCES 

For  a  discussion  of  this  test  see  Sherman's  "  Organic  Analysis," 
and  for  the  probable  composition  of  the  colored  compound  formed  on 

132 


LABORATORY  EXPERIMENTS  133 

the  test  paper,   see  Richter's   "Organische   Chemie,"    n.  Auflage, 
Vol.  II,  713- 

QUESTIONS 

1.  W  'te  the  stereo  structures  of  the  different  possible  pentoses, 

and  name  them. 

2.  What  substance  is  formed  by  the  action  of  hydrochloric 

acid  on  a  pentose? 

3.  What  are  the  pentoses  obtained  from  gum  arabic,  cherry 

gum,  corn  cobs,  bran,  etc.? 

4.  To  what  class  of  cyclic  compounds  does  furfural  belong? 

5.  What  is  a  pentosan? 

6.  How  can  pentoses  be  obtained  from  the  pentosans? 

7.  Name  some  substances  which  are  or  contain  pentosans. 

8.  Compare  the  pentosans  with  starch  and  cellulose. 

9.  What  is  a  galactan? 

10.  What  is  the  phloroglucinol  test  for  furfural? 

11.  How  can  the  phloroglucinol  test  be  used  for  the  quantitative 

estimation  of  pentoses?     (See  Sherman's  "  Organic  Anal- 
ysis.") 

12.  Show  how  arabinose  can  be  converted  into  glucose. 

13.  Show  how  glucose  can  be  converted  into  arabinose. 

14.  What  is  a  pentonic  acid?    How  prepared? 


Experiment  No.  36 

OXIDATION  or  A  SUGAR 

Mucic  Acid  from  Lactose 

In  a  porcelain  dish,  13-14  cm.  in  diameter,  evaporate  over  a 
free  flame 'a  solution  of  12  grams  of  lactose  in  150  grams  of  nitric 
acid1  of  sp.gr.  1.15  to  a  volume  of  about  25  cc.  with  stirring 
towards  the  end.  In  order  to  remove  the  fumes  support  a  large 
funnel  over  the  dish  and  connect  it  with  the  suction  pump.  Do 
not  heat  so  strongly  that  the  material  is  charred  on  the  sides 
of  the  evaporating  dish.  Brown  fumes  (?)  are  evolved,  and 
the  mass  finally  becomes  thick  and  pasty  owing  to  the  separa- 
tion of  mucic  acid.  When  cold,  dilute  with  water,  filter  with 
suction,  and  wash  with  small  amounts  of  cold  water.  In  order 
to  determine  the  yield  of  crude  product,  dry  it  on  a  watch  glass 
on  the  steam-bath  or  in  an  oven. 

To  purify,  dissolve  the  crude  dry  material  in  a  cold  solution 
of  sodium  hydroxide  and  re-precipitate  with  hydrochloric  acid. 
Only  the  neutral  salt  is  easily  soluble  in  water,  and  its  solubility 
is  decreased  by  excess  of  alkali.  (?)  It  is  best  therefore  to 
calculate  approximately  the  amount  of  N/2  sodium  hydroxide 
solution  necessary.  Do  not  add  dry  solid  sodium  hydroxide  to 
the  water  containing  the  mucic  acid — use  a  cold  solution.  Filter 
if  necessary.  If  the  solution  is  dark  brown,  decolorize  by  gently 
warming  with  animal  charcoal,  or  filter  through  a  funnel  con- 
taining animal  charcoal.  Cool  and  add  the  equivalent  of  5N 
hydrochloric  acid2  to  set  free  the  mucic  acid.  The  hydro- 

1  The  calculations  can  be  made  from  the  following  data:    The  specific  gravity 
of  ordinary  cone,  nitric  acid  is  1.42. 

Nitric  acid,  1.15,  contains  24.84%  HNO3  by  weight  (15°) 
Nitric  acid,  1.42,  contains  69.80%  HNO3  by  weight  (15°) 

2  Cone,  hydrochloric  acid,  sp.  gr.  1.19,  contains  37%  HC1  by  weight  (15°). 

134 


LABORATORY  EXPERIMENTS  135 

chloric  acid  must  not  be  added  while  the  liquid  is  warm  because 
part  of  the  mucic  acid  may  be  converted  into  the  easily  soluble 
lactone.  To  complete  the  crystallization,  allow  the  liquid  to 
stand,  then  filter  with  suction,  wash  with  cold  water,  and  dry. 
Yield,  4  grams.  Determine  the  melting-point.  (?)  Mucic 
acid  is  soluble  one  part  in  100  of  water  at  14°. 

Try  the  action  of  Fehling's  solution  on  lactose.  What  does 
this  indicate? 

NOTE 

The  term  "mucic"  comes  from  the  Latin  word  "mucus,"  mean- 
ing mucus  or  slime.  Mucic  acid  has  been  known  for  many  years, 
having  early  been  prepared  by  the  action  of  nitric  acid  on  some  plant 
mucilaginous  material  which  contained  galactans.  The  German 
name  for  mucic  acid  is  "Schleimsaure." 

QUESTIONS 

1.  Write  the  equations  for  all  reactions  involved  in  the  pro- 

duction of  mucic  acid  from  lactose,  indicating  the  various 
reactions  by  means  of  stereochemical  structures. 

2.  Explain  why  it  is  necessary  to  use  nitric  acid  of  about  this 

particular  strength,  and  give  reasons. 

3.  What  is  the  action  of  cone,  nitric  acid  on  lactose? 

4.  What  significance  is  there  in  the  fact  that  lactose  reduces 

Fehling's  solution? 

5.  Which  of  the  two  mono-saccharides  combined  in  the  lactose 

molecule  contains  the  "  free  "  carbonyl  group?  How  can 
this  be  shown?  (The  structural  formula  of  lactose  in 
Stoddard,  "  Introduction  to  Organic  Chemistry,"  2d  Ed., 
p.  215,  should  be  reversed.)  Compare  Holleman's 
"  Organic  Chemistry." 

6.  What  becomes  of  the  saccharic  acid  and  how  does  it  differ 

from  mucic  acid  structurally?    Is  it  optically  active? 

7.  Can  you  give  any  reason  why  you  would  expect  mucic  acid 

not  to  have  the  same  solubility  as  saccharic  acid? 

8.  Is  this  acid  named  d,  /,  racemic  or  meso  mucic  acid?     Give 

reasons. 

9.  What  is  the  salt  formed  when  sodium  hydroxide  reacts  with 

mucic  acid?     Name? 

10.  Why  is  it  necessary  to  neutralize  so  carefully  with  sodium 
hydroxide? 


136          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

11.  Write  the  structure  of  the  lactone  of  mucic  acid. 

12.  To  what  class  of  organic  compounds  do  the  lac  tones  belong? 

13.  Are  compounds  like  the  lactones  often  formed  by  boiling 

water? 

14.  Indicate  the  difference  between  an  "  acid  lactone  "  and  a 

"  sugar  lactone." 

15.  What  is  the  chief  organic  impurity  removed  by  the  re- 

crystallization  and  washing?     Is  this  obtained  from  other 
sugars  likewise? 


Experiment  No.  37 
Cellulose  Acetate 

In  a  small  Erlenmeyer  flask  place  20  cc.  of  glacial  acetic 
acid,  6  cc.  of  acetic  anhydride,  2  drops  of  cone,  sulfuric  acid, 
and  0.5  gram  of  absorbent  cotton.  Press  the  cotton  into  the 
solution  with  a  glass  stirring-rod,  and  after  a  few  minutes  stir 
it  so  that  most  of  the  air  bubbles  are  removed.  Stopper  and  let 
it  stand  overnight  or  longer.  Pour  the  clear  solution  which  is 
obtained  in  a  thin  stream,  and  with  stirring,  into  500  cc.  of  water. 
Filter  with  suction,  using  a  large  funnel.  Press  out  between 
filter  paper  or  on  a  porous  tile  until  dry.  Put  about  one-half 
the  dry  product  in  a  small  beaker  or  test-tube  and  add  20  cc.  of 
chloroform.  After  standing  some  time  the  acetate  should  pass 
into  solution.  Pour  the  solution  upon  a  watch  glass  and  let  it 
evaporate  slowly.  When  the  chloroform  has  evaporated,  put 
some  water  into  the  watch  glass  and  allow  it  to  stand  for  a 
minute  or  two.  Lift  the  edge  of  the  film  and  remove  it  slowly 
from  the  glass.  Dry  the  film  and  try  its  burning  qualities. 
Test  the  solubility  of  the  remainder  of  the  acetate  in  glacial 
acetic  acid,  in  alcohol,  and  in  ether. 

QUESTIONS 

1.  How  is  cellulose  related  to  the  simple  sugars? 

2.  Outline,  in  general,  the  reaction  with  acetic  anhydride. 

3.  What  conclusion  as  to  the  groups  in  cellulose  can  you  draw 

from  this  reaction? 

4.  How  does  cone,  sulfuric  acid  affect  cellulose? 

5.  How  does  a  mixture  of  cone,  nitric  and  sulfuric  acids  react 

with  cellulose? 

6.  What  is  a  "  tetra-nitrate,"  a  "  hexa-nitrate  "  of  cellulose? 

7.  What  is  smokeless  powder?     Celluloid?     Collodion? 

8.  How  is  artificial  silk  made? 

9.  What  is  viscose?     Explain  its  formation  and  use. 

10.  What  is  mercerized  cotton? 

11.  Compare  the  action  of  the  reagents  mentioned  in  questions 

2,  4,  and  5  on  starch. 

137 


Experiment  No.  38 
BENZENE:     CHEMICAL  PROPERTIES 

a.  To  2  cc.  of  benzene,  labeled  "  thiophene  free,"  add  0.5  cc. 
of  a  dilute  solution  of  bromine  in  carbontetrachloride.     Does  the 
color  of  the  bromine  disappear  immediately?    At  all? 

b.  (Hood.)     Add  several  drops  of  bromine   (not  bromine 
water)   to  5  cc.  of  benzene.     Divide  the  solution  into  equal 
portions,  and  to  one  add  some  iron  powder.     Note  the  differ- 
ence in  the  velocity  of  the  reaction  in  the  two  tubes.     Breathe 
across  the  top  of  them.     (?) 

c.  Add  several  drops  of  benzene  to  i  cc.  of  cone,  sulfuric 
acid.     Shake.     Is  there  any  evidence  of  chemical  action  apparent 
by  the  formation  of  heat  or  by  darkening?     Does  the  mixture 
become  homogeneous?     Pour  it  into  6  cc.  of  cold  water,  cool, 
stir,  and  then  transfer  to  a  No.  i  test-tube.     Is  a  homogeneous 
solution  obtained?    Does  benzene  dissolve  in  hot  cone,  sulfuric 
acid? 

d.  Repeat  c.,  using  fuming  sulfuric  acid.    Pour  the  mixture 
drop  by  drop  into  cold  water  or  better,  upon  ice.     Result? 
(A  solid  substance,  diphenylsulfone,  may  separate  in  the  water 
solution.     Explain.) 

e.  Add  several  drops  of  benzene  to  i   cc.  of  cone,  nitric 
acid.     Shake  well  for  two  minutes.    Any  heat  formed?    Then 
add  slowly  with  cooling  i  cc.  of  cone,  sulfuric  acid.     Shake. 
Any  change?    Pour  into  cold  water  and  stir  well.    What  is  the 
heavy  yellow  oil  that  settles  out  in  droplets?    Note  the  odor. 

Is  benzene  reacted  upon  by  fuming  nitric  acid?    Try  it. 

/.  To  i  cc.  of  a  very  dilute  solution  of  potassium  perman- 
ganate in  a  small  glass-stoppered  bottle,  add  i  cc.  of  benzene 
("  thiophene  free  ").  Is  there  any  change  noticeable? 

138 


LABORATORY  EXPERIMENTS  139 

Compare  all  the  above  reactions  with  benzine  (in  the  Methane 
experiment,  p.  31)  and  pinene  (in  the  Ethylene  experiment,  p.  45). 

g.  Determine  the  freezing-point  of  benzene  by  freezing  some 
in  a  test-tube  placed  in  ice  and  water.  Stir  the  benzene  with  a 
thermometer  until  it  solidifies.  Note  any  super-cooling  also. 

The  true  freezing-point  of  benzene  is  5.483.°  See  Richards 
and  Shipley,  "  The  Freezing-point  of  Benzene  as  a  Fixed  Point 
in  Thermometry,"  Journ.  Amer.  Chem.  Soc.,  36  (1914),  1825. 

h.  Small  quantities  of  aromatic  hydrocarbons  are  conveniently 
identified  by  converting  them  into  solid  nitro  derivatives,  usually 
the  di-nitro- compound,  and  determining  the  melting-point. 

Mix  i  cc.  of  cone,  sulfuric  acid  and  i  cc.  of  cone,  nitric  acid 
in  a  dry  test-tube  and  add  three  drops  of  benzene.  Heat  to 
boiling  and  boil  for  thirty  seconds.  Cool  and  pour  slowly  into 
10  cc.  of  water  in  another  test-tube.  Shake.  Filter  off  the 
bulky  precipitate  with  suction,  collecting  it  upon  a  small  filter  l 
and  wash  until  the  washings  are  no  longer  colored.  Dissolve  the 
substance  with  shaking  in  a  boiling  mixture  of  4  cc.  of  alcohol 
and  4  cc.  of  water  and  set  aside  to  crystallize.  It  crystallizes 
in  long  fine  needles  which  are  nearly  white.  Filter  with  suction 
and  allow  to  dry  upon  a  porous  tile.  Determine  the  melting- 
point  of  the  w-dinitrobenzene  formed,  which  should  be  89.72  cor.2 

Write  the  structure  of  the  compound  formed  in  this  reaction. 
Can  a  similar  compound  of  toluene  be  prepared  with  the  same 
kind  of  acid  mixture? 

HISTORICAL  NOTE 

Faraday,  in  1825,  discovered  a  liquid  hydrocarbon  in  compressed  coal-gas 
which  he  called  "bicarburet  of  hydrogen,"  since  it  had  the  empirical  formula 
CzH.  (on  the  basis  of  the  atomic  weight  of  carbon  being  6  which  was  used  at  that 
time).  Mitscherlich,  1834,  obtained  the  same  hydrocarbon  by  the  distillation  of 
benzoic  acid  with  slaked  lime  and  termed  it  "benzin."  He  assumed  that  it  was 
formed  from  the  benzoic  acid  by  the  removal  of  CO2.  Liebig  denied  this,  adding 
the  following  editorial  note  to  Mitscherlich's  memoir  in  the  "Annalen":  "We 
have  changed  the  name  of  the  body  obtained  by  Prof.  Mitscherlich  by  the  dry 
distillation  of  benzoic  acid  and  lime  and  termed  by  him  benzin,  into  benzol,  because 

1  For  nitration  of  small  quantities  with  suction,  see  p.  56. 

2  For  this  method  of  preparation,  see  Mulliken,  "Identification  of  Pure  Organic 
Compounds,"  Vol.  I,  200. 


140          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

the  termination  'in'  appears  to  denote  an  analogy  between  strychnine  (German, 
strychnin)  and  quinine,  etc.,  bodies  to  which  it  does  not  bear  the  slightest  resem- 
blance, whilst  the  ending  in  'ol '  corresponds  better  to  its  properties  and  mode  of 
production.  It  would  have  been  better  perhaps  if  the  name  which  the  discoverer, 
Faraday,  had  given  to  this  body  had  been  retained,  as  its  relation  to  benzoic  acid 
and  benzoyl  compounds  is  not  any  closer  than  it  is  to  that  of  the  tar  or  coal  from 
which  it  is  obtained."  A.  W.  Hofmann,  in  1845,  isolated  the  hydrocarbon  from 
coal-tar.  Later  the  name  benzene  came  into  use  in  accordance  with  the  ending  of 
unsaturated  hydrocarbons. 

For  many  years,  however,  the  ending  "ol"  has  been  used  to  denote  an  alcohol 
or  a  phenol.  The  term  benzol  is,  therefore,  considered  a  hybrid  and  a  misnomer. 
Unfortunately  the  pronunciation  of  benzene  is  the  same  as  that  of  benzine — one 
of  the  petroleum  fractions,  but  this  can  be  remedied  by  using  benzolene  instead  of 
benzine  (see  Note  i,  p.  33). 

REFERENCES 

Roscoe  and  Schorlemmer,  "Treatise  on  Chemistry,"  Vol.  Ill,  Pt.  Ill  (1897), 
64;  and  "Resolution  Concerning  Organic  Nomenclature,"  Journ.  Ind.  and  Eng. 
Chem.,  10  (1918),  944. 


Experiment  No.  39 

FITTIG'S  SYNTHESIS  OF  AN  AROMATIC  HYDROCARBON 

Preparation  of  Ethylbenzene  from  Benzene  and  Ethyl 
Bromide 

Weigh  out  12  grams  of  metallic  sodium  in  lumps  from  which 
all  the  crust  has  been  removed.  Use  a  common  knife  or  a  pen- 
knife and  dip  the  blade  frequently  into  the  kerosene  with  which 
the  sodium  is  covered.  Return  all  residues  to  the  original 
bottle.  Put  the  sodium  into  a  dry  200  cc.  round-bottomed 
flask  and  cover  with  30  cc.  of  commercial  xylene.  Attach  an 
addition  tube  and  bulbed  condenser  with  sealed  joints  x  as  a 
reflux  condenser.  Stopper  the  tube  and  heat  the  flask  gently 
over  a  wire  gauze  until  the  sodium  melts  (m.p.  95.6°,  the  xylene 
boils  at  i36°-i4i°).  Do  not  heat  the  xylene  to  boiling.  On 
account  of  the  crust  which  forms  about  the  sodium  while  exposed 
to  the  air,  it  often  appears  that  the  sodium  does  not  melt  because 
the  melted  globules  are  held  by  this  covering.  Disconnect  while 
hot,  stopper  the  flask  with  a  good  cork,  place  a  folded  towel 
•at  the  bottom  of  the  flask  and  another  at  the  top  to  protect  the 
hands,  hold  the  flask  in  an  upright  position  and  shake  vigorously 
in  a  vertical  line  for  a  moment  until  the  sodium  is  broken  into 
small  globules — "  bird-shot  "  sodium.  Let  the  flask  rest  upon  a 
suberite  ring2  until  cold.  Do  not  shake  too  long,  since  the 
melted  sodium  may  form  one  large  lump.  Now  decant3  the 
xylene  into  a  dry  beaker  and  quickly  wash  the  sodium  twice  by 
decantation  with  20  cc.  portions  of  dry  ether  ("  absolute  ether  " 

1  If  a  condenser  with  rubber  connections  is  used,  the  joints  must  be  wired 
to  make  them  perfectly  tight. 

2  A  suberite  ring  is  a  ring  of  pressed  cork  for  supporting  round-bottomed 
flasks. 

3  Do  not  decant  the  xylene  or  the  ether  into  a  wet  beaker  or  into  the  sink.  Par- 
ticles of  sodium  may  thus  come  in  contact  with  water.    Destroy  the  sodium  by 
adding  alcohol. 

141 


142         LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

or  "  ether  over  sodium  ").  Add  50  cc.  of  dry  ether  and  re- 
assemble the  apparatus,  setting  the  flask  in  a  beaker.  In 
twenty  to  thirty  minutes  the  ether,  which  is  very  hygroscopic 
and  cannot  ordinarily  be  kept  dry,  will  be  dry  enough  and 
practically  no  more  bubbles  will  be  given  off.  Now  pour 
through  the  addition  tube  a  mixture  of  30  grams  (20  cc.)  of 
brombenzene  and  30  grams  (20  cc.)  of  ethyl  bromide  (an  excess 
of  the  theoretical  amount) ,  and  let  stand  overnight.  If  the  liquid 
begins  to  boil  vigorously  cool  by  pouring  cold  water  into  the 
beaker.  It  should  be  watched  for  about  an  hour  before  leaving 
the  laboratory.  Do  not  allow  the  water  to  run  through  the 
condenser  outside  of  laboratory  hours! 

During  the  reaction  the  sodium  is  changed  to  a  blue  powder 
and  an  ethereal  solution  of  ethylbenzene  is  formed.  The  next 
day  remove  the  ether  by  distillation  observing  the  ordinary 
precautions.  The  ether  is  practically  all  distilled  when  no  more 
drops  come  over.  Dry  the  outside  of  the  flask,  connect  it  in  an 
inclined  position,  with  the  extreme  end  of  the  neck  clamped 
loosely,  to  an  air  condenser  with  adapter  attached  leading  into 
a  receiver  and  loosely  plug  the  annular  space  in  the  mouth  of 
the  receiver  with  cotton.  Distill  the  crude  ethylbenzene  from 
the  apparently  dry  residue  by  heating  with  a  luminous  flame 
which  is  kept  in  constant  motion.  Toward  the  end  of  the  dis- 
tillation the  heat  may  be  increased.  Since  the  ether  is  not 
entirely  removed  in  the  first  distillation  care  must  be  taken  in 
this  operation  and  the  eyes  should  be  protected  with  goggles. 

Then  subject  the  crude  product  to  at  least  two  fractionations. 
Use  a  small  distilling  flask  and  place  into  it  a  piece  of  pumice 
or  tiling  to  aid  ebullition.  Carefully  heat  the  flask  directly  with 
a  very  small  flame.  Collect  separately  the  portions  boiling  below 
115°,  between  ii5°-i4o°  and  above  140°.  Redistill  each  portion, 
collecting  as  the  sample  the  part  boiling  between  i33°-i36°. 
The  boiling-point  of  pure  ethylbenzene  is  135.98°  (760  mm.) 1 
cor.  It  is  "of  great  advantage  in  this  fractionation  to  use  a 
small  round-bottomed  flask  surmounted  by  a  Young  four-pear 
still  head,  see  Fig.  4,  p.  25.  Yield,  8  grams. 

1 T.  W.  Richards  and  F.  Barry.   Journ.  Amer.  Chem.  Soc.,  37  (1915),  998. 


LABORATORY  EXPERIMENTS  143 

The  residue  in  the  original  flask  contains  some  sodium 
and  must  be  handled  with  care.  Remove  the  material  and 
add  it  in  small  pieces  to  ethyl  alcohol  or  acetone  in  a  beaker, 
waiting  until  all  the  sodium  in  each  piece  has  been  destroyed 
before  adding  another.  Dilute  with  water  (Care!)  before  pour- 
ing the  solution  into  the  sink.  Rinse  out  the  flask  with  alcohol 
before  adding  any  water. 

Sometimes  crude  amyl  alcohol  is  used  for  destroying  sodium 
residues.  Its  action  is.  much  slower,  and,  furthermore,  globules  of 
sodium  are  often  found  at  the  end  of  the  main  reaction  coated 
with  sodium  amyl  oxide,  and  their  presence  is  sometimes  not 
noticed  until  after  water  has  been  added! 

QUESTIONS 

1.  Of  what  does  the  crust  on  the  sodium  consist? 

2.  Name  some  other  liquids  that  might  be  used  to  cover  the 

sodium  in  the  bottle. 

3.  Why  must  the  xylene  be  removed  after  making  the  "  bird- 

shot  "  sodium? 

4.  Compare  the  molecular  and  structural  formulas  of  ethyl 

benzene  and  the  xylenes. 

5.  How  could  you  distinguish  chemically  between  the  isomers, 

ethyl  benzene  and  w-xylene? 

6.  Why  not  add  the  brombenzene   and   the  ethyl  bromide 

separately? 

7.  Why  must  you  wait  until  the  ether  is  dry  before  proceeding? 

8.  What  two  other   organic   compounds   are  formed  in   this 

reaction?    What  becomes  of  them? 

9.  Is  the  reaction  applicable  to  the  aliphatic  series? 

10.  What  is  the  object  of  the  ether?    Why  is  the  "  ether  over 

sodium  "  used?     What  other  substances  could  be  used? 

11.  Why  must  the  condenser  be  perfectly  tight? 

12.  Why  does  not  all  the  ether  come  over  in  the  first  distillation, 

since  it  boils  at  35°? 

13.  Why  is  the  flask  dried  after  the  distillation  of  the  ether? 

14.  Why  is  the  flask  inclined? 

15.  What  is  the  cause  of  the  blue  color? 

1 6.  Why  is  the  luminous  flame  kept  in  constant  motion? 

17.  Write  the  structure  of  the  compounds  formed  when  ethyl 

alcohol  and  sodium,  and  amyl  alcohol  and  sodium  react. 

18.  Outline  an  apparatus  for  heating  a  reaction  mixture  above  its 

boiling-point  in  a  flask.     (Gattermann,  p.  280.) 


Experiment  No.  40 

SYNTHESIS    OF   AN  -AROMATIC   HYDROCARBON  BY  MEANS  OF 
FRIEDEL-CRAFTS'  REACTION 

Preparation   of   Diphenylmethane  from  Benzene   and   Benzyl 

Chloride 

I 

Attach  an  addition  tube  and  dry  reflux  condenser  to  a  dry 
300  cc.  flask.  Connect  the  top  of  the  condenser  with  a  tube 
leading  into  the  draft  pipe.  Put  60  cc.  of  benzene,  and  17  cc. 
of  benzyl  chloride  1  into  the  flask.  Weigh  out  5  grams  of  finely- 
pulverized  anhydrous  aluminium  chloride2  in  a  dry  test-tube 
closed  by  a  cork  and  add  this  in  two  portions  (the  second  after 
the  first  reaction  has  subsided)  to  the  mixture  in  the  flask.  Let 
stand  until  the  evolution  of  hydrogen  chloride  has  nearly  stopped 
(thirty  minutes).  Then  disconnect  the  apparatus  and  add 
40  grams  of  finely  ground  ice.  (?)  Shake,  and  after  the  ice 
has  melted,  separate  the  layers  in  a  separatory  funnel.  The 
upper  layer  of  benzene  contains  the  diphenylmethane,  and  after 
the  lower  layer  has  been  drawn  off  pour  the  upper  layer  from 
the  top  of  the  funnel. 

In  order  to  remove  the  benzene  most  quickly  and  also  leave 
the  crude  diphenylmethane  in  a  small  flask  ready  for  the  final 
fractionation,  the  solution  is  fractionated  in  portions  under 
diminished  pressure  or  in  vacua  as  follows:  Connect  a  125  cc. 
Claisen  and  an  ordinary  distilling-flask  for  distillation  in  vacua 

1  The  vapors  of  benzyl  chloride  are  very  irritating  to  the  eyes  and  the  mucous 
membranes  of  the  nose  and  mouth. 

2  The  sealed  bottles  in  which  the  anhydrous  aluminium  chloride  comes  often 
contain  considerable  pressure.    Great  care  is  therefore  necessary  in  opening  them. 
Use  the  method  described  on  p.  33,  and  completely  wrap  the  bottle  in  a  towel 
before  striking  the  neck  above  the  file  mark  a  blow  with  the  file.    The  aluminium 
chloride  must  be  in  good  condition  or  the  experiment  will  be  a  failure. 

144 


LABORATORY  EXPERIMENTS  145 

(Expt.  15,  p.  76),  fill  the  upright  one  not  more  than  one- third 
full  of  the  solution,  and,  keeping  the  bath  4o°-5o°,  distill  until 
practically  all  the  benzene  and  water  have  gone  over.  Equalize 
the  pressure  by  slowly  opening  the  stop-cock,  take  away  the  bath, 
cool,  then  add  more  of  the  solution.  Continue  these  operations 
until  all  the  benzene  and  water  have  been  removed.  The  last 
time  raise  the  temperature  and  stop  the  distillation  when  the 
diphenylmethane  begins  to  distill.  Attach  a  clean  receiving- 
flask  and  then  distill  the  residue.  By  keeping  the  temperature 
of  the  oil-bath  constant  where  the  diphenylmethane  distills 
regularly  no  trouble  with  excessive  foaming  will  be  experienced. 
If  the  product  is  colored  or  does  not  completely  solidify,  redistill 
in  vacua  after  adding  two  or  three  small  pieces  of  sodium. 
(Why?)  Destroy  the  sodium  in  the  residue  with  alcohol.  At 
22  mm.  pressure  diphenylmethane  boils  at  145°  (at  760  mm., 
263°).  It  is  a  clear  heavy  liquid  which  crystallizes  to  a  solid 
white  mass  of  needles  on  standing  in  the  refrigerator  or  after 
adding  a  crystal  of  the  substance  ("  seeding  ").  M.  p.,  2^-26°. 
It  is  partially  decomposed  when  distilled  under  ordinary  atmos- 
pheric pressure,  and  has  an  odor  resembling  that  of  orange- 
peel.  Yield,  15  grams. 

QUESTIONS 

1.  Why  is  the  aluminium  chloride  weighed  out  in  a  closed 

test-tube? 

2.  What  causes  the  initial  brown  color  when  the  Aids  is 

added? 

3.  What  is  the  purpose  of  the  ice? 

4.  What  becomes  of  the  aluminium  chloride? 

5.  Why  is  the  product  distilled  in  vacuo? 

6.  Is  there  any  advantage  in  removing  the  benzene  in  vacuo? 

7.  Why  is  the  benzene  distilled  off  in  portions  in  a  small  flask? 

8.  What  other  possible  compounds  are  formed  in  the  reaction 

and   remain  in   the   "  tar  "   in   the   fractionating  flask? 
(Compare  Gattermann,  p.  323.) 

9.  At  the  end  of  the  distillation  of  the  diphenylmethane  the 

temperature  often  drops  considerably  although  the  bath 
is  still  at  a  high  temperature.     Explain. 


146          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

10.  What  other  class  of  compounds  can  be  made  by  the  Friedel- 

Crafts  reaction? 

11.  Diphenylme thane  on  oxidation  with  chromic  acid  mixture 

yields  benzophenone.  Is  this  reaction  general  with 
aromatic  hydrocarbons?  Compare  triphenylme thane  and 
diphenyl. 

12.  What  kind  of  halogen  derivatives  are  used  in  the  Friedel- 

Crafts  reaction,  aliphatic  or  aromatic,  or  both? 

13.  Would  there  be  any  reaction  between  brombenzene  and 

benzene  in  the  presence  of  aluminium  chloride? 

14.  How  could  you  prepare  triphenyl-me thane? 

15.  From  its  structure  would  you  expect  diphenylmethane  to 

be  soluble  in  benzene? 

1 6.  Discuss  the  use  of  the  aluminium-mercury  couple  in  place 

of  the  aluminium  chloride  for  preparing  diphenylmethane, 
etc.  (J.  B.  Cohen,  "  Organic  Chemistry  for  Advanced 
Students,"  Pt.  I,  2d  Ed.  (1918),  198;  and  Norris,  "  Experi- 
mental Organic  Chemistry  "  (1915),  p.  132.) 


Experiment  No.  41 

FORMATION  or  A  FREE  RADICAL 
Triphenylmethyl 

Place  0.5  gram  of  triphenylchlormethane  1  and  i  gram  of 
powdered  zinc  into  a  clean,  dry,  No.  i  test-tube.  Seal  a  glass 
rod  in  the  open  end,  soften  the  glass  near  this  end  in  the  blast 
flame  and  draw  it  out  to  a  narrow  tube  about  2  mm.  in  diameter 
(compare  sealing  of  a  bomb  tube,  p.  117).  When  cold,  pour  in 
4  cc.  of  dry  benzene2  and  after  letting  it  drain  well  seal  off 
the  end  of  the  tube.  (Care!)  Shake  and  allow  it  to  remain 
in  a  horizontal  position  for  two  days.  The  heavy  brown  oil 
which  separates  on  the  bottom  is  a  double  compound  of  tri- 
phenylmethyl  and  zinc  chloride.  At  the  end  of  the  time  specified 
open  the  tube  and  quickly  divide  its  contents  into  two  test-tubes. 
Have  ready  a  solution  of  iodine  in  benzene  and  immediately  test 
ithe  unsaturated  nature  of  the  compound  by  slowly  adding  the 
iodine  solution.  (?)  The  other  portion  rapidly  absorbs  oxygen 
from  the  air  and  the  insoluble  triphenyl-methyl -peroxide  is 
precipitated. 

REFERENCE 

Gomberg,  "The  Existence  of  Free  Radicals,"  Journ.-  Amer. 
Chem.  Soc.,  36  (1914),  1144-70. 

1  Triphenylchlormethane  must  be  kept  in  sealed  bottles,  since  it  will  slowly  be 
hydrolyzed  by  moisture  in  an  ordinary  cork-stoppeied  bottle. 

2  If  the  tube  is  so  narrow  that  the  benzene  does  not  flow  down  readily,  alter- 
nately warm  the  lower  part  of  the  tube  with  the  hand,  and  cool,  when  the  liquid 
will  be  drawn  into  the  tube  in  small  portions.     Sometimes  it  will  run  down  easily 
if  the  tube  is  inclined  and  the  liquid  poured  in  very  slowly. 

147 


148         LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 


QUESTIONS 

1.  Is  there  any  objection  to  the  use  of  a  larger  test-tube  in  this 

experiment? 

2.  Why  must  dry  benzene  be  used? 

3.  Explain  the  ready  absorption  of  iodine  by  the  solution. 

4.  Write  the  formula  for  the  compound  formed  when  the  solu- 

tion is  exposed  to  the  air. 

5.  Compare  some  of  the  higher  homologues  of  triphenylmethyl 

with  triphenylmethyl  itself,  in  regard  to  physical  and 
chemical  properties.  (See  Journ.  Amer.  Chem.  Soc.,  36 
(1914),  1165-6.) 

6.  Discuss  the  question  of  the  existence  of  free  radicals. 


Experiment  No.  42 

HALOGENATION  OF  AN  AROMATIC  HYDROCARBON 
Preparation  of  Brombenzene 

NOTE. — This  experiment  must  be  allowed  to  stand  overnight,  but  not  longer 
than  two  or  three  days,  since  the  monobrombenzene  first  formed  is  gradually 
converted  into  higher  bromination  products. 

Into  a  200  cc.  flask  containing  two  small  iron  nails  place 
20  cc.  of  benzene  and  13  cc.  (42  grams)  of  bromine  (draft  pipe). 
Immediately  attach  a  reflux  condenser  with  top  connected  with 
the  draft  pipe  by  means  of  a  tube.  In  a  short  time  an  energetic 
action  will  begin,  generally  spontaneously,  with  the  evolution 
of  hydrogen  bromide.1  If  necessary,  warm  slightly  to  start  the 
reaction.  Let  stand  overnight.  Add  water  to  the  flask  and 
wash  twice  by  decantation,  then  in  a  separatory  funnel  wash  with 
dilute  sodium  hydroxide  solution2  until  the  liquid  is  no  longer 
acid,  and  again  with  water.  Separate  the  liquids  (sp.  gr.  of 
brombenzene  is  1.489  at  21°),  dry  with  calcium  chloride,3  and 
distill,  using  an  air  condenser  (p.  15).  Collect  the  portion 
boiling  between  i4o°-i7o°  and  fractionate  this  two  or  three 
times  narrowing  the  limits  each  time,  collecting  finally  the  por- 
tion between  154-6°.  The  boiling-point  of  pure  mono-brom- 
benzene  is  155.5°  cor-  Yield,  18  grams. 

The  crystals  which  are  sometimes  present  in  the  original 
flask  and  the  residue  boiling  above  170°  in  the  distilling-flask 

1  This  is  a  good  method  for  preparing  hydrobromic  acid  by  absorption  of  the 
gas  in  water. 

2  If  an  emulsion  is  formed,  it  can  be  "broken"  by  making  the  mixture  slightly 
acid  with  hydrochloric  or  sulfuric  acid. 

3  If  sufficient  water  has  been  extracted  by  the  calcium  chloride  to  form  a  solu- 
tion of  the  salt  sometimes  floating  on  the  surface  of  the  liquid,  separate  this  aque- 
ous layer  and  add  fresh  calcium  chloride.    (Why  is  this  necessary?) 

149 


150          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

consist  mainly  of  ^-dibrombenzene.  Dissolve  this  material  in 
10-20  cc.  of  hot  alcohol  and  filter  the  hot  solution.  If  the 
filtrate  is  not  water- white  decolorize  by  adding  animal  charcoal, 
in  small  amounts  to  avoid  excessive  foaming  of  the  hot  liquid, 
cover  with  a  watch  glass,  heat  on  the  steam-bath  for  several 
minutes,  and  filter  again  while  hot.  Set  the  beaker  aside  for 
crystallization.  Finally  filter  off  the  crystals  of  ^-dibrombenzene 
with  suction,  dry  and  determine  the  melting-point.  (?) 

a.  Repeat  experiment  c  under  ethyl  iodide   (p.  38)   using 
only  a  portion  of  a  drop  of  brombenzene.     Result? 

b.  Repeat  the  same  experiment  using  benzyl  chloride. 

c.  Repeat   the   above   experiments,  but  use  distilled  water 
in  place  of  the  alcohol.     Do  not  mistake  an  emulsion  for  a  pre- 
cipitate.   Compare  results  with  those  with  the  alcoholic  solution. 

QUESTIONS 

1.  What  is  the  object  of  the  iron  nails?    Why  not  use  iron 

filings?     Under  what  condition  could  the  latter  be  used? 

2.  What  dibrom  product  is  obtained  in  the  experiment?     Are 

any  of  the  other  two  possible  dibrom  products  formed  at 
all? 

3.  Why  should  the  reaction  mixture  not  be  allowed  to  stand 

more  than  one  or  two  days  after  the  bromine  has  been 
added? 

4.  What  is  the  reddish-brown  precipitate  sometimes  formed 

when  the  sodium  hydroxide  solution  is  added? 

5.  How  is  benzyl  bromide  prepared? 

6.  What  are  alpha-  and  beta-benzene    hexabromides?     (J.    B. 

Cohen,    "  Organic   Chemistry   for   Advanced   Students," 
Pt.  II,  2d  Ed.  (1918),  260-3.)     How  prepared? 

7.  What  advantages  has  a  separatory  funnel  over  decantation, 

and  decantation  over  a  separatory  funnel,  for  washing 
purposes? 

8.  Compare  the  stability  toward  hydrolyzing  reagents  of  the 

aryl  halides  with  the  alkyl  halides. 

9.  What  compounds,  if  any,  are  formed  by  the  action  of  alcoholic 

KOH   on  benzyl   chloride;    on   i-phenyl-2-chlorpropane; 
picryl  chloride;  brombenzene? 

10.  How  can  brombenzene  be  converted  into  benzene?    Into 
diphenyl? 


LABORATORY  EXPERIMENTS  151 

11.  Give  some  of  the  modifications  in  the  methods  of  using 

bromine  for  brominations. 

12.  Give   methods   for   preparing    chlorbenzene    from    aniline; 

from  chlorbenzoic  acid;  and  for  benzyl  iodide  from  benzyl 
chloride. 

13.  How  are  the  iodo-derivatives  prepared? 

14.  Explain  the  action  of  the  boneblack  in  decolorizing  the  solu- 

tion of  dibrombenzene. 


Experiment  No.  43 

SULFONATION   OF   AN   AROMATIC   HYDROCARBON 

Preparation  of  Benzene  Sulfonic  Acid,  Sodium  Salt 

To  5  cc.  of  fuming  sulfuric  acid  in  a  test-tube,  add  in  small 
portions  3  cc.  of  benzene,  shaking  vigorously  and  cooling  after 
each  addition.  When  the  benzene  has  all  dissolved  and  the  liquid 
is  clear,  slowly  pour  it  into  20  cc.  of  water  in  a  flask,  cooling  it 
under  running  water.  Filter  off  with  suction  any  diphenyl- 
sulfone  which  separates.  Partly  neutralize  by  adding  4  grams 
of  crystalline  sodium  carbonate,  then  add  5  grams  of  common 
salt.  Warm  and  stir  till  it  dissolves,  filter  while  hot  through  a 
fluted1  filter  paper,  and  cool.  Stir  well  when  the  solution  is  almost 
cold.  The  sodium  benzene-sulfonate  separates  out  in  a  mass  of 
white  lustrous  plates.  It  may  be  necessary  to  set  the  beaker 
in  ice  in  order  to  promote  and  complete  the  crystallization. 
Filter  with  suction.  Press  as  dry  as  possible  while  it  is  in  the 
funnel.  Allow  to  dry  on  filter  paper  or  press  out  on  a  porous 
plate.  Recrystallize  from  hot  alcohol.  The  pure  sodium  salt 
melts  at  about  450°.  Such  a  melting-point  cannot  be  taken  with 
the  ordinary  apparatus.  Yield,  4  grams. 

NOTES 

1.  A  greenish  color  often  develops  during  the  sulfonation.    This 
usually  disappears  in  the  recrystallization  from  alcohol. 

2.  Sometimes  the  material  does  not  crystallize  out  of  the  alco- 
holic solution  very  well.    Possibly  a  soluble  "alcoholate"  similar  to 
a  "hydrate"  is  formed.    Evaporation,  thorough  cooling,  and  stirring 
generally  overcome  the  difficulty. 

1  See  foot-note,  p.  128. 
152 


LABORATORY  EXPERIMENTS  153 


QUESTIONS 

1.  What  is  fuming  sulfuric  acid? 

2.  Could  cone,  sulfuric  acid  be  used?     How? 

3.  Account  for  the  formation  of  the  diphenyl-sulfone.     Would 

a  lesser  amount  of  sulfuric  acid  tend  to  increase  or  di- 
minish the  amount  formed? 

4.  Why  is  the  mixture  partly  neutralized  with  sodium  car- 

bonate? 

5.  Is  it  necessary  to  use  the  sodium  carbonate  for  the  forma- 

tion of  the  sodium  benzene-sulfonate  which  crystallizes 
out,  or  would  the  sodium  salt  be  formed  and  precipi- 
tated by  adding  sodium  chloride  alone? 

6.  How  could  you  filter  a  fuming  sulfuric  acid  solution? 

7.  What  impurities  does  the   sodium  benzene-sulfonate  con- 

tain before  recrystallization? 

8.  How  may  the  product  be  freed  from  these  impurities  (No.  7)? 

9.  Explain  the  formation  of  the  sodium  salt  of  benzene  sulfonic 

acid  by  the  theory  of  "  salting  out." 
How   are    the    corresponding    calcium   and   barium   salts 

prepared? 
rn.  How  is  the  free  sulfonic  acid  obtained  from  these  salts 

(No.  10)? 
^2.  How  is  the  free  sulfonic  acid  obtained  from  the  lead  salt? 

13.  What  mono-sulfo  derivatives  of  naphthalene  are  prepared 

by  direct  sulfonation? 

14.  Compare  the  structures  of  the  sulfonic  acids  and  of  the 

nitro-compounds  with  relation  to  the  acids  from  which 
they  are  derived. 

15.  How  can  the  sulfo-acids  be  converted  into  the  parent  hydro- 

carbon? 

1 6.  How  can  the  sulfo  group  be  replaced  by  OH,  by  CN? 

*  These  questions  are  not  required  for  study  in  the  "short"  course. 


Experiment  No.  44 

NITRATION  OF  AN  AROMATIC  HYDROCARBON 
Preparation  of  Nitrobenzene 

In  a  flask  carefully  mix  18  cc.  of  cone,  nitric  acid  and  18  cc. 
of  cone,  sulfuric  acid,  cooling  under  running  water  after  each 
addition  of  one  acid  to  the  other.  When  the  solution  has  come 
to  the  room  temperature  add  it  slowly  from  a  dropping-funnel  to 
13  cc.  of  benzene  contained  in  an  open  300  cc.  flask,  under  the 
hood.  (Do  not  use  any  cork  or  rubber  connection.)  Shake  well 
and  cool  frequently  under  running  water,  keeping  the  temperature 
of  the  liquid  below  50°.  When  all  the  mixture  has  been  added, 
half  immerse  the  flask  in  water  maintained  at  50°  by  means  of 
steam  or  a  burner  kept  burning  low  and  let  it  remain  at  this 
temperature  for  thirty  minutes  connected  with  a  tube  leading 
to  the  draft  pipe.  Since  the  mixture  separates  into  layers  on 
standing,  it  must  be  shaken  occasionally  during  the  heating. 
The  nitration  is  complete  when  a  drop  which  is  added  to  water 
sinks  to  the  bottom.  The  presence  of  any  unchanged  benzene 
will  cause  it  to  float.  In  performing  this  test  stir  well  to  make 
certain  that  any  drops  on  the  surface  are  not  held  up  by  surface 
tension  alone. 

Pour  the  contents  of  the  flask  into  about  500  cc.  of  water 
in  another  flask,  shake  thoroughly,  cool  it,  and  separate  the  lower 
turbid  yellow  layer  of  nitrobenzene  by  means  of  a  separatory 
funnel.  Return  it  to  the  funnel  and  wash  the  oil  with  sodium 
hydroxide  solution  until  free  from  acid,  and  finally  wash  with 
water.  Separate  as  completely  as  possible  and  return  the  oil  to 
a  dry  separatory  funnel.  Add  calcium  chloride  and  shake.  If 
an  aqueous  solution  of  the  salt  separates,  remove  it  and  add  fresh 
calcium  chloride.  Repeat,  and  then  transfer  the  liquid  to  a  small 

154 


LABORATORY  EXPERIMENTS  155 

Erlenmeyer  flask,  add  several  pieces  of  fresh  calcium  chloride, 
stopper,  and  allow  to  stand  overnight  to  complete  the  drying. 
Be  sure  to  clean  the  separatory  funnel  so  that  the  stopper  and 
stop-cock  will  not  stick.  It  is  well  to  keep  the  parts  separated, 
but  tied  with  a  piece  of  twine.  When  dry  the  nitrobenzene  will 
be  clear.  Filter  through  a  funnel  as  usual  containing  a  plug 
of  glass  wool  into  a  dry  distilling-flask  with  low  outlet  tube 
(style  C).  The  stem  of  the  funnel  should  reach  below  the  open- 
ing of  the  delivery  tube.  Distill.  Catch  the  first  runnings, 
which  consist  chiefly  of  benzene  and  traces  of  water,  direct  from 
the  outlet  tube.  When  the  clear  yellowish  nitrobenzene  begins  to 
distill  attach  a  dry  air  condenser  and  distill,  using  a  dry  weighed 
specimen  bottle  as  the  receiver.  Do  not  in  any  case  allow  the 
temperature  to  go  more  than  5°  above  the  boiling-point:  the 
residue  sometimes  decomposes  explosively.1  B.p.  210.9°  cor- 
Yield,  17  grams. 

NOTE 

Nitrobenzene  is  a  poison.  Its  vapor  should  not  be  breathed 
excessively  and  it  should  not  be  allowed  to  remain  in  contact  with 
the  skin. 

QUESTIONS 

1 .  Can  nitrobenzene  be  prepared  by  adding  benzene  to  the  acid 

mixture,  instead  of  the  acid  mixture   to  the  benzene? 
Why  is  the  method  used  in  the  laboratory  preferred? 

2.  What  compound  is  formed  if  the  temperature  is  allowed 

to  rise  much  above  50°? 

3.  What  is  the  object  of  the  sulfuric  acid? 

4.  What  compounds  are  formed  by  the  "  nitronation  " 2  of 

toluene?     Under  what  conditions  does  toluene  yield  ben- 
zoic  acid  when  treated  with  nitric  acid? 

1  This  is  most  likely  to  happen  when  the  product  contains  polynitro  derivatives 
and  also  nitro  derivatives  of  homologues  of  benzene  if  a  good  quality  of  benzene 
was  not  used. 

2  The  word  "nitration"  at  present  stands  for  the  formation  of  both  a  true 
nitro  derivative  like  nitrobenzene  and  of  a  nitrate  like  the  cellulose  nitrates.    The 
term  "nitronation"  is  suggested  for  the  formation  of  a  nitro  derivative  just  as 
"sulfonation"  stands  for  the  formation  of  a  sulfo  derivative  in  a  similar  manner, 


156          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

5.  Name    some    important    classes    of    nitro-compounds    and 

indicate  their  uses. 

6.  Why  must  nitrobenzene  not  be  heated  above  its  boiling- 

point? 

7.  How  are  most  nitro-compounds  purified? 

8.  Are  different  products  obtained  when  nitrobenzene  is  chlo- 

rinated and  when  chlorbenzene  is  nitrated? 

9.  How  are  the  conditions  of  nitration  varied?     Compare  the 

preparation  of  nitrobenzene  and  of  nitrophenol. 

10.  What  is  the  general  chemical  influence  of  the  nitro-group? 

11.  How  are   the   aliphatic  nitro-compounds   prepared?     Two 

methods. 

12.  How    is    phenyl-nitro-methane    prepared?     Why    is    this 

soluble  in  alkali? 

13.  Compare  the  structure  of  nitro-compounds  and  the  isomeric 

nitrites; 

14.  What  are  the  products  of  the  reduction  of  nitro-compounds 

and  of  nitrites? 

15.  What  is  a  pseudo-acid? 

1 6.  How  are  the  alpha-  and  beta-mono-nitronaphthalenes  pre- 

pared? 

17.  How  can  the  three  different  classes  of  aliphatic  mono-nitro 

compounds  be  distinguished? 


Experiment  No.  45 

REDUCTION  OF  A  NITRO-COMPOUND  TO  AN  AMINE 
Preparation  of  Aniline  from  Nitrobenzene 

To  15  grams  of  nitrobenzene  and  35  grams  of  granulated  tin, 
contained  in  a  500  cc.  flask  with  a  vertical  air  condenser  attached, 
add  in  small  portions  100  cc.  of  cone,  hydrochloric  acid.  Shake 
the  flask  frequently.  The  mixture  will  become  so  warm  that 
the  reaction  must  be  controlled  by  occasionally  cooling  the  flask, 
but  not  enough  to  prevent  the  liquid  from  boiling  quietly.  After 
the  first  50  cc.  of  acid  .have  been  added  the  second  may  be  added 
in  larger  amounts  of  about  15  cc.  with  the  same  precautions. 
In  order  to  effect  the  complete  reduction  of  the  nitrobenzene  the 
mixture  is  finally  heated  for  one-half  hour  on  the  steam-bath. 
The  reaction  mixture  must  be  watched  when  first  heated  on  the 
steam-bath,  since  if  it  were  kept  so  cold  in  the  beginning  that  the 
reaction  was  cut  down  too  much,  it  will  now  suddenly  become 
so  violent  that  the  unreduced  nitrobenzene  and  the  hydrochloric 
acid -will  be  driven  out  of  the  tube  of  the  condenser.  During  the 
reaction  (and  especially  when  cooled)  the  double  salt  of  aniline 
hydrochloride  and  stannic 1  chloride  (CeHsNH^HCl^,  SnCU, 
separates  out  as  a  white  crystalline  solid.  At  the  end  of  the 
operation  when  the  odor  of  nitrobenzene  has  entirely  disappeared, 
and  a  drop  of  the  reaction  mixture  gives  a  clear  solution  in  water 
(Why?),  add  enough  water  to  dissolve  the  salt,  cool  thoroughly, 
then  pour  off  this  solution  from  any  unused  tin  into  a  separatory 
funnel.  If  any  of  the  salt  separates  on  cooling  add  more  water  to 
dissolve  it.  Extract  the  liquid  twice  with  60  cc.  portions  of 
ether,  following  the  directions  on  p.  74.  Remember  when 

1  Stannous  chloride  forms  a  similar  double  salt,  and  a  mixture  is  obtained  here, 

157 


158          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

working  with  ether  to  keep  away  from  free  flames!  Ether  boils 
at  35°,  has  a  very  high  vapor  pressure,  and  is  very  inflammable. 
Finally  draw  off  the  aqueous  layer  into  a  flask.  The  ethereal 
extracts  should  be  discarded. 

(If  the  entire  experiment  cannot  be  completed  at  one  time 
it  should  be  interrupted  at  this  point  in  order  that  the  neutrali- 
zation with  sodium  hydroxide  may  be  directly  followed  by  the 
steam  distillation,  and  the  heat  of  neutralization  thereby 
utilized.) 

The  free  amine  (aniline)  is  obtained  from  the  double  salt  in 
the  extracted  acid  solution  by  adding  gradually  a  solution  of 
about  50  grams  of  sodium  hydroxide  in  90  cc.  of  water.  Stannic 
and  stannous  hydroxides  form  at  first  and  partially  dissolve. 
The  precipitate  may  be  entirely  dissolved  by  adding  more  sodium 
hydroxide,  but  this  is  not  necessary.  The  mixture  should  have  a 
strongly  alkaline  reaction.  (Why?)  If  boiling  occurs  during 
the  addition  of  the  alkali,  cool  the  solution  under  running  water 
before  adding  more.  (Why?)  Most  of  the  aniline  rises  to  the 
top  as  an  oil.  . 

The  aniline  could  now  be  extracted  with  ether,  but  this  is 
not  advisable,  since  the  alkaline  solution  forms  a  difficultly 
separable  emulsion  with  the  ether. 

Distillation  with  Steam.1  The  free  aniline  is  separated  by 
steam  distillation,  using  the  apparatus  shown  in  Fig.  13. 

Steam  is  passed  into  the  flask  through  a  tube  which  is  bent 
in  such  a  way  that  it  reaches  almost  to  the  bottom  (Why?) 
when  the  flask  is  inclined.  (Why  is  the  flask  inclined?)  The 
outlet  tube  should  be  cut  off  just  beneath  the  stopper  (?)  and 
the  bend  should  be  just  above  the  stopper.  (Why?)  The  outlet 
tube  also  should  be  of  a  larger  diameter  than  the  inlet  tube.  (?) 
The  flask  should  not  be  more  than  half  full  when  the  distillation 
is  begun.  Use  a  long  water  condenser.  Make  the  rubber  con- 
nections as  short  as  possible  and  attach  the  rubber  tube  to  the 

1  References  for  the  principles  involved  in  distillation  with  steam:  Morgan, 
"The  Elements  of  Physical  Chemistry,"  5th  Ed.  (1918),  177-8;  Smith,  "Introduc- 
tion to  Inorganic  Chemistry,"  ^d  Ed.  (1917),  563;  Walker,  "Introduction  to 
Physical  Chemistry,"  7th  Ed.  (1913),  87, 


LABORATORY  EXPERIMENTS  159 

inlet  tube  of  the  flask  in  such  a  way  that  it  can  easily  and  quickly 
be  removed  if  occasion  demands.  Set  the  flask  into  a  Babo- 
funnel l  or  upon  a  wire  gauze,  and  heat  gently  during  the  opera- 
tion. (?)  It  is  well  to  wrap  a  towel  around  the  upper  part  of 
the  flask  (?).  If  the  steam  is  passed  into  the  solution  when  cold 
a  "  cracking  "  sound  is  often  heard.  This  disappears  as  soon  as 
the  liquid  becomes  hot. 

The  steam  on  the  desk  can  be  used  as  the  supply.     Since 
there  is  always  considerable  condensation  water,  a  500  cc.  flask 

•5 f earn  frvm 
the  /aborafory 
Supp/y 


for  5fea/r?  Dist///afion 

FIG.  13. 

should  be  placed  as  a  trap  between  the  steam  nozzle  and  the 
apparatus.  Use  a  three-holed  stopper  in  this  flask.  The  inlet 
and  outlet  tubes  should  be  cut  off  just  below  the  stopper.  Into 
the  third  hole  pass  a  glass  tube  leading  to  the  bottom  of  the 
flask,  bent  downwards  above  the  stopper  and  connected  with  a 
piece  of  rubber  tubing  to  act  as  a  siphon.  Use  a  screw  clamp 
to  shut  off  the  siphon.  When  the  flask  is  nearly  filled  with 
water  open  the  clamp  and  the  water  will  go  out  and  it  is  not  neces- 
sary to  stop  the  distillation  during  this  time.  If  the  screw  clamp 

1  A  Babo-funnel  is  an  iron  funnel  partially  lined  with  strips  of  asbestos,  and  is 
often  used  in  place  of  an  iron  gauze. 


160          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

is  partly  opened  and  properly  adjusted  the  water  will  pass  out 
regularly  without  requiring  further  attention. 

Or  steam  can  be  generated  in  an  ordinary  tin  oil-can,  pro- 
vided with  a  safety  tube  50  cm.  long;  the  spout  is  used  for  the 
outlet.  Or  a  flask  may  be  used  with  a  safety  tube  and  outlet 
tube.  The  safety  tube  should  extend  almost  to  the  bottom, 
and  if  a  wide  one  is  used,  such  as  a  condenser  tube,  it  will  also 
serve  for  pouring  in  the  water,  especially  when  the  "  boiler  " 
is  hot  (although  in  such  a  case  the  "  boiler  "  must  not  be  con- 
nected with  any  apparatus  when  the  water  is  being  added 
unless  boiling  water  is  used). 

The  distillation  is  considered  complete  when  no  more  oily 
drops  come  over  in  the  distillate  (i  to  i^  hours) .  Remove  the  rub- 
ber connection  from  the  main  flask  before  turning  off  the  steam 
or  extinguishing  the  flame.  Collect  about  300  cc.  of  the  cloudy 
distillate.  Some  of  the  aniline  separates  as  an  oil  at  the  bottom 
of  the  receiver.  Toward  the  end  of  the  distillation,  just  after 
the  oily  drops  have  ceased  to  come  over,  collect  separately 
2  cc.  of  the  clear  distillate  and  make  the  following  two  tests  for 
dissolved  aniline. 

To  one  portion  add  some  bromine  water.  What  is  the 
white  precipitate? 

To  another  portion  add  a  small  amount  of  a  filtered  water 
solution  of  good  bleaching  powder.  (?) 

Ether  Extraction.  Saturate  the  steam  distillate  contained 
in  a  liter  separatory  funnel  with  powdered  sodium  chloride, 
25  grams  for  every  100  cc.  of  liquid.  Then  extract  the  aniline 
with  ether,  using  three  successive  portions  of  ether,  50  cc.  at  first, 
then  30  cc.  and  30  cc.  Test  a  portion  of  the  aqueous  solution 
after  the  ether  extractions  to  see  if  any  aniline  remains,  in 
same  manner  that  you  tested  the  steam  distillate  above.  Dry 
the  combined  ethereal  solutions  in  an  Erlenmeyer  flask  by 
adding  two  or  three  small  sticks  of  solid  sodium  hydroxide. 
Stopper  the  flask  with  a  cork  and  let  stand  overnight.  If  an 
aqueous  solution  of  sodium  hydroxide  forms  at  the  bottom, 
the  layers  should  be  separated,  fresh  sodium  hydroxide  added, 
and  the  mixture  allowed  to  stand  overnight  again.  (?)  (Cal- 


LABORATORY  EXPERIMENTS  161 

cium  chloride  cannot  be  used  for  drying  in  this  case  because  it 
forms  a  double  compound  with  aniline.) 

Distillation. — In  order  that  the  small  amount  of  aniline 
remaining  after  the  removal  of  the  ether  may  be  left  in  a  small 
flask  for  the  final  distillation,  the  ether  is  distilled  over  in  the 
following  manner:  Attach  a  dropping  funnel  to  a  50  cc  distilling 
flask.  The  stem  of  the  funnel  should  reach  into  the  bulb  of  the 
flask.  Put  in  one  or  two  pieces  of  porous  tile.  Do  not  add  these 
after  the  "olution  has  become  warm  since  it  may  cause  violent 
ebullition  with  loss  of  solution  by  overflow  and  imminent  danger 
of  fire.  Connect  the  outlet  tube  with  a  straight  water  condenser 
and  attach  an  adapter  to  the  lower  end  of  the  condenser  by  means 
of  a  cork.  In  order  to  avoid  circulation  of  ether  vapors  loosely 
plug  the  remaining  space  in  the  mouth  of  the  receiver  with 
cotton.  Add  the  ethereal  solution  to  the  flask  until  it  is  one- 
third  full.  Heat  the  flask  gently  over  the  steam-bath  and 
continue  the  addition  at  about  the  same  rate  at  which  the  ether 
distills. 

When  all  the  ether  is  distilled  over,  disconnect  the  apparatus 
and  remove  the  ether  distillate.  Dry  the  outside  of  the  dis- 
tilling-flask.  (Why?)  Insert  a  thermometer,  connect  with  a 
dry  air  condenser,  and  distill  the  aniline,  using  a  small  free 
flame.  Since  there  may  be  some  ether  remaining  in  the  flask 
the  initial  heating  should  be  Carefully  done.  Collect  the  pure 
aniline  in  a  dry  weighed  specimen  bottle.  It  boils  at  184.4° 
cor.;  its  specific  gravity  is  1.02^5;  and  100  cc.  of  water  dis- 
solves 3.48  cc.  of  aniline  at  22°,  and  100  cc.  of  aniline  dissolves 
5.22  cc.  of  water  at  22°.  When  pure  it  is  a  colorless,  oily, 
strongly  refracting  liquid,  which  becomes  yellow  and  red  on 
standing,  especially  when  in  the  presence  of  air,  and  light,  and 
possesses  a  peculiar  odor  common  to  many  amines.  Yield, 
10  grams. 

a.  Shake  a  drop  of  pure  aniline  with  a  few  cubic  centimeters 
of  pure  distilled  water  (ammonia  free),  and  test  the  clear  solution 
with  a  piece  of  neutral  litmus  paper.     What  is  the  reaction? 

b.  Add  some  of  this  solution  to  a  solution  of  ferric  chloride, 
and  of  zinc  chloride.     In  view  of  the  reaction  shown  in  a,  how  do 


162         LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

you  account  for  the  observation  which  you  have  made  with 
these  salt  solutions? 

c.  Dissolve  two  or  three  drops  of  aniline  in  the  least  possible 
amount  of  dilute  hydrochloric  acid.     Why  does  aniline  dissolve 
easily  in  acids  while  it  is  soluble  with  difficulty  in  water?    Neu- 
tralize with  sodium  hydroxide  solution.     (?) 

d.  To  four  or  five  drops  of  cone,  sulfuric  acid  in  a  small 
porcelain  evaporating  dish  add  a  drop  of  aniline  on  a  stirring- 
rod.     What  is  the  white  solid  formed?    Now  add  two  or  three 
drops  of  a  water  solution  of  sodium  dichr ornate  and  stir.     (?) 
Compare    Holleman,   "  Organic    Chemistry,"  4th  Ed.    (1914), 


e.  Add  two  or  three  drops  of  nitrobenzene  to  0.5  cc.  of 
aniline.  Note  the  deep  red  color  that  is  formed.  (Compare 
Biron  and  Morguleva,  "  Color  of  Mixtures  of  Anilines  with 
Aromatic  Nitro  Compounds."  Journ.  Russ.  Phys.  Chem.  Soc.y 
46  (1914),  1598;  Chem.  Abstracts,  9  (1915),  2069. 

QUESTIONS 

1.  Write  the  equation  for  the  reduction  of  nitrobenzene. 

2.  Explain  why  only  a  little  acid  is  necessary  in  the  production 

of  aniline  commercially  from  nitrobenzene  by  means  of  iron 
as  the  reducing  agent. 

3.  Why  is  not  all  the  hydrochloric  acid  added  at  one  time  when 

the  nitrobenzene  is  reduced  by  tin  and  hydrochloric  acid? 

4.  Calculate  the  amount  of  hydrochloric  acid  necessary  for  this 

experiment. 

5.  What  is  the  nature  of  the  salt  formed  from  stannic  chloride 

and   aniline  hydrochloride?     How  would  this  salt  behave 
in  a  water  solution? 

6.  Is  there  any  difference  between  a  double  salt  and  a  complex 

salt? 

7.  Why  is  it  necessary  to  cool  before  extracting  the  nitro- 

benzene with  ether?     What  is  the  principle  underlying 
ether  extraction? 

8.  What  does  the  ether  extract  contain  and  why  is  it  desirable 

to  perform  this  extraction? 

9.  Could  any  other  method  be  used  in  place  of  the  ether  extrac- 

tion? 


LABORATORY  EXPERIMENTS  163 

10.  How  does  sodium  hydroxide  react  with  the  double  salt? 

Write  all  equations  for  this  chemical  change. 

11.  Show   how   aniline   hydrochloride   can   be    converted   into 

aniline,  writing  the  equation  from  the  ionic  standpoint. 

12.  Why  is  it  necessary  to  be  careful  in  adding  the  sodium 

hydroxide  solution  to  the  solution  of  the  double  salt? 
Explain  why  the  liquid  becomes  hot. 

13.  What  is  the  gray  precipitate  that  forms  when  a  large  excess 

of  sodium  hydroxide  has  been  used?     Account  for  it. 
Jr/        (References,    Mellor,    "  Modern    Inorganic    Chemistry," 
790-1,  and  Ditte,  Ann.  Chem.  Phys.  [5],  27  (1882),  145.) 

14.  Discuss  fully  the  principles  involved  in  steam  distillation. 

15.  How  can  you  tell  by  chemical  means  when  all  the  aniline 

has  been  distilled  over  with  steam? 

1 6.  Why  not  continue  the  steam  distillation  until  the  distillate 

gives  no  test  for  aniline? 

17.  Does  aniline  react  alkaline  toward  litmus?    Is  it  a  true 

base? 

18.  In  a  short  time  after  the  steam  distillation  has  begun  a 

considerable  amount  of  aniline  collects  in  the  receiver, 
and  by  the  time  the  distillation  is  completed  practically 
all  this  aniline  has  disappeared.  Explain. 

19.  During  the  steam  distillation  some  of  the  aniline  collects 

at  the  bottom  of  the  receiver,  some  floats  on  the  water. 
Explain. 

20.  Explain  why   aniline   hydrochloride  is   not   volatile   with 

steam  while  aniline  is. 

21.  Would  you  expect  phenyl  ammonium  hydroxide  to  be  vola- 

tile with  steam? 

22.  What  is  the  object  of  adding  sodium  chloride  to  the  steam 

distillate  before  the  ether  extraction? 

23.  Explain  why  the  ether  solution  is  dried  with  solid  sodium 

hydroxide  instead  of  calcium  chloride  or  anhydrous 
sodium  sulfate.  Could  the  latter  be  used? 

24.  Why  is  no  jacket  necessary  for  the  condenser;   would  it  do 

any  harm  if  a  condenser  jacket  were  used? 

25.  Point  out  the  relationship  between  the  double  salt  of  stannic 

chloride  and  aniline  hydrochloride,  and  ammonium  chlor- 
platinate. 


Experiment  No.  46 

ACETYLATION   OF   AN   AROMATIC   AMINE 

Preparation  of  Acet-0-toluidide  from  0-Toluidine 

To  5  cc.  of  acetic  anhydride  l  in  a  125  cc.  Erlenmeyer  flask, 
add  2  drops  of  cone,  sulfuric  acid.  Then  add  slowly  in  small 
portions,  with  shaking  and  cooling  under  running  water  after  each 
addition,  4  cc.  of  0-toluidine.  Allow  the  mixture  to  stand  at 
room  temperature  for  one-half  hour  or  longer.  The  entire  product 
then  appears  like  a  solid  mass.  If  it  does  not  solidify,  scratch 
the  inside  wall  of  the  vessel  with  a  glass  rod  to  promote  crystal- 
lization. Now  add  30  cc.  of  water  and  warm  on  the  steam- 
bath.  This  loosens  the  product  and  with  the  aid  (careful!)  of  a 
stirring-rod  disintegrate  and  transfer  it  to  a  250  cc.  flask.  Make 
the  volume  up  to  160  cc.,  using  some  of  this  water  to  rinse  out 
the  flask.  Neutralize  with  ammonium  hydroxide  solution. 
(Why  not  NaOH?)  Heat  the  flask  on  the  steam-bath  until 
solution  takes  place.  Generally  a  pink  solution  is  obtained. 
Sometimes  the  substance  melts  and  collects  at  the  bottom  of 
the  flask.  Shake  to  dissolve  it.  Decolorize  by  adding,  in  small 
amounts,  two  spoonfuls  of  animal  charcoal.  Continue  the  heat- 
ing for  about  twenty  minutes,  with  occasional  shaking,  then 
filter  while  hot  through  a  large  fluted  filter  in  a  hot-water  funnel 
(see  p.  128),  and  set  the  solution  aside  to  crystallize.  If  the 
crystals  obtained  are  colored  they  should  be  re-dissolved  as  before 
in  hot  water  and  heated  again  with  animal  charcoal.  Filter 
off  the  needle-like  crystals  with  suction  by  means  of  a  Buchner 
funnel  and  let  them  dry  between  filter  papers,  or  in  a  desiccator, 
or  press  them  out  on  a  porous  tile.  Concentrate  the  filtrate  on 

1  Acetic  anhydride  attacks  the  skin  and  the  mucous  membranes.    Be  careful 
in  handling  it. 

164 


LABORATORY  EXPERIMENTS  165 

the  steam-lath  to  about  30  cc.  volume,  decolorize,  if  necessary, 
filter  as  before,  and  allow  to  cool.     M.  p.,  110°.    Yield,  5  grams.1 

a.  Heat   some   of    the   crystals   of   acet-0-toluidide   with   a 
strong  solution  of  sodium  hydroxide.     What  is  formed?    Boil  a 
few  crystals  with  dilute  sulfuric  acid  (i  :  i).     Notice  the  odor 
of  the  vapor.  (?) 

b.  To  2  cc.  of  acetyl  chloride  add  i  cc.  of  0-toluidine  carefully. 
Warm  and  treat  the  product  with  water.     Separate  the  crystals 
and   recrystallize   the   substance   from   a  little  boiling  water. 
Compare  the  melting-point  of  these  crystals  with  the  melting- 
point  of  a  sample  of  the  acet-0-toluidide  prepared  above. 

c.  .Grind  together  small  dry  portions  of  the  pure  acet-0- 
toluidide  obtained  in  the  main  experiment  and  of  the  substance 
prepared  in  0,  and  determine  the  melting-point  of  the  mixture. 
If  the  substances  were  not  of  the  same  chemical  composition 
would  the  melting-point  of  the  mixture  be  the  same  even  though 
each  substance  originally  had  the  same  melting-point? 

d.  Warm  i  cc.  of  acetyl  chloride  with  i  cc.  of  mono-methylanil- 
ine;  then  heat  i  cc.  of  acetyl  chloride  with  i  cc.  of  dimethylanil- 
ine.     Pour  each  product  into  water.     Is  there  evidence  of  chemi- 
cal change  in  each  case?     Are  the  reactions  illustrated  in  b  and 
d  typical  of  primary,  secondary,  and  tertiary  amines  in  general? 

REFERENCES 

W.  M.  Dehn,  "  Acetylations  in  Ether  Solutions,"  Jour.  Amer. 
Chem.  Soc.,  34  (1912)  1399;  Dehn  and  Ball,  "  Benzoylations  in 
Ether  Solutions,"  ibid.,  36  (1914)  2091. 

NOTE 

Solutions  of  organic  compounds  should  seldom  be  evaporated 
over  a  free  flame.  If  any  evaporation  is  necessary  in  the  above 
experiment  use  a  steam-bath.  At  low  temperatures  there  is  the  least 
decomposition,  and  for  this  reason  it  is  often  best  to  evaporate  under 
diminished  pressure. 

1  This  amount  is  too  much  for  the  usual  preparation  bottle  to  contain.  Hand 
in  a  sample,  stating  the  total  yield  on  the  label,  and  use  the  major  portion  for  the 
preparation  of  acetanthranilic  acid  (p.  189). 


166         LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 


QUESTIONS 

1.  Compare  the  structures  of  acetic  anhydride,  acetyl  chloride, 

and  acetyl  sulfuric  acid.     How  is  the  anhydride  prepared? 

2.  Explain  the  use  of  the  "  two  drops  of  cone,  sulfuric  acid." 

3.  Why  is  it  necessary  to  neutralize  the  solution? 

j..  What  product  is  neutralized  with  ammonium  hydroxide? 

5.  What  objection  would  there  be  to  the  use  of  sodium  hydrox- 

ide?    Could  it  be  used  at  all? 

6.  Why  is  a  hot- water  funnel  used?     Why  must  the  stem  of  the 

funnel  not  project  much  below  the  metal  collar? 

7.  By  means  of  structural  formulas  show  how  acet-0-toluidide 

differs  from  0-toluidine  acetate. 

8.  What  would  be  obtained  by  heating  dry  ammonium  acetate? 

dry  0-toluidine  acetate?     Compare  No.  9. 

9.  To'  what  class  of  organic  compounds  does  acet-0-toluidide 

belong? 

*io.  What  advantage  has  acetic  anhydride  over  acetyl  chloride 
for  acetylation? 

11.  How  is  aniline  acetylated  commercially?    Use  of  product? 

12.  Do   3°-amines    react    at    all    with   acetyl   chloride?      (See 

special  references  above.) 

*i3.  What  is  the  structure  of  diacetanilide?     How  prepared? 
*i4.  Of  what  use  in  the  laboratory  is  the  acetylation  of  amines? 

*  These  questions  are  not  required  for  study  in  the  "short"  course. 


Experiment  No.  47 

SULFONATION   OF   AN   AROMATIC  AMINE 

Preparation  of  Sulfanilic  Acid  from  Aniline 

Pour  50  grams  of  cone,  sulfuric  acid  into  a  100  cc.  round- 
bottomed  flask,  then  attach  an  air  condenser,  and  through  it 
add  cautiously  with  moderate  shaking  15  grams  of  aniline. 
Do  not  shake  so  vigorously  that  the  sulfuric  acid  comes  in  contact 
with  the  upper  portion  of  the  flask  or  the  lower  part  of  the  air 
condenser.  The  first  reaction  product  (?)  deposited  at  these 
places  is  not  easily  got  down  into  the  main  portion.  Half 
immerse  the  flask  in  an  oil-bath,  which  consists  of  a  shallow 
iron  dish  partly  filled  with  rapeseed  oil,1  and  heat  the  mixture 
of  aniline  sulfate  and  sulfuric  acid  at  a  temperature  of  175°- 
i8o°,2  thermometer  in  the  oil,  for  three  hours.  Pour  the  par- 
tially cooled  product  with  stirring  into  about  250  cc.  of  cold 
water,  when  the  sulfanilic  acid  will  separate  out  in  crystals. 
Allow  to  stand  for  about  twenty-four  hours,  then  filter  off  the 
product  with  suction  in  a  Buchner  funnel.  Wash  once  with  a 
little  cold  water. 

Suspend  the  crystals  thus  obtained  in  100  cc.  of  water  and 
dissolve  them  by  adding  a  2N  solution  of  sodium  hydroxide  until 
neutral  to  litmus.  If  the  solution  is  water-white  filter  from 
any  impurities,  otherwise  heat  to  boiling,  decolorize  by  heating 
for  about  half  an  hour  on  the  water-bath  with  the  addition  of 
animal  charcoal  (added  in  small  quantities  to  prevent  foaming) 
and  filter.  Precipitate  the  sulfanilic  acid  in  the  filtrate  by 
adding  the  calculated  amount  of  hydrochloric  acid  (based 

1  Do  not  allow  any  water  to  come  in  contact  with  the  hot  oil.    It  causes  violent 
foaming.     Compare  note  6,  p.  82. 

2  A  higher  temperature  causes  considerable  decomposition.    The  heating  may 
be  interrupted  at  any  time. 

167 


168          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

on  the  theoretical  yield)  to  liberate  the  acid  from  its  sodium 
salt.  Allow  to  stand  overnight,  filter  with  suction,  wash  with  a 
little  water,  and  dry  the  crystals  between  filter  paper.  Large 
rhombic  plate  crystals  may  be  obtained  by  dissolving  the  sulf- 
anilic  acid  in  just  the  sufficient  amount  of  hot  water  for  com- 
plete solution  and  allowing  to  cool  slowly.  The  crystals  con- 
tain 2  molecules  of  water  of  hydration,  which  is  slowly  lost 
in  the  air  and  the  crystals  fall  to  a  powder.  They  are  soluble 
in  hot  water  but  not  very  soluble  in  cold  water.  Yield,  15  grams. 
It  has  no  definite  melting-point,  but  decomposes  28o°-3oo°. 

QUESTIONS 

i..  What  is  the  white  solid  first  formed? 

2.  If  necessary,  how  could  you  filter  the  hot  acid  solution? 

3.  Name  sulfanilic  acid  to  show  its  chemical  groups  and  their 

position. 

4.  Trace  the  changes  from  the  compound  first  formed  through 

the  amide-form  and  the  rearrangement  to  sulfanilic  acid. 
(See  J.  B.  Cohen,  "  Organic  Chemistry  for  Advanced 
Students,"  Pt.  II,  2d  Ed.  (1918),  371.) 

5.  Why  must  the  mixture  not  be  heated  above  180°? 

6.  How  could  a  test  be  made  to  show  that  all  the  aniline  has 

been  converted  into  the  sulfanilic  acid? 

7.  Why  must  an  excess  of  sodium  hydroxide  be  avoided? 

8.  If  you  have  added  an  excess  of  sodium  hydroxide  in  trying 

to  make  the  solution  neutral  how  could  you  treat  the  solu- 
tion in  order  to  obtain  all  the  sulfanilic  acid? 

9.  Although  sulfanilic  acid  is  soluble  in  hot  water  the  material 

is  bone-blacked  in  an  alkaline  solution.     Why? 

10.  Explain  the  action  of  bone  black  (animal  charcoal). 

11.  Why  must  the  calculated  amount  of  HC1  be  used?     Why  not 

simply  add  HC1  to  acid  reaction? 

12.  What  is  naphthionic  acid? 

13.  Compare  the  chemical  properties  of  the  amino  sulfonic  acids 

and  the  amino  carboxylic  acids. 

14.  What  use  is  made  of  sulfanilic  and  similar  acids? 

15.  How  can  the  meta-compound  corresponding  to  sulfanilic 

acid  be  prepared? 


Experiment  No.  48 
Benzidine  Rearrangement 

Dissolve  2  grams  of  powdered  sodium  hydroxide  in  20  cc. 
of  alcohol  in  a  large  (No.  3)  test-tube.  Add  2  cc.  of  nitrobenzene 
and  warm  gently.  During  the  course  of  several  minutes  add, 
in  small  quantities,  about  5  grams  of  zinc  dust.  At  first  the  solu- 
tion becomes  deep  red  in  color.  This  is  due  to  the  formation 
of  azo-benzene.  Later  this  color  is  discharged  on  account  of  the 
formation  of  hydrazo-benzene.  Sometimes  instead  of  a  color- 
less solution  a  light  brown  solution  is  obtained.  Then  pour 
the  mixture  into  about  50  cc.  of  water  containing  more  than 
enough  sulfuric  acid  to  neutralize  the  sodium  hydroxide  used. 
(Why?)  A  colorless  or  slightly  yellow  precipitate  of  benzidine 
sulfate  separates.  There  should  be  no  oil  (?)  floating  upon  the 
surface. 

QUESTIONS 

1 .  Write  the  structures  of  the  compounds  formed  in  this  reaction. 

2.  Are  all  sulfates  of  mono-  and  di-amines  insoluble  in  water? 

3.  How  could  you  prepare  pure  benzidine  from  this  salt? 

4.  Tabulate  some  important  reactions  in  which  it  is  believed  the 

"  benzidine  rearrangement  "  takes  place.  (Ex.,  />-amino- 
phenol  from  phenyl  hydroxylamine,  />-phenylenediamine 
from  phenyl  hydrazine,  sulfanilic  acid  from  the  amide  of 
aniline  sulfate,  salicylic  acid  from  sodium  phenolate  and 
carbon  dioxide,  amino-azobenzene  from  azo-amino-benzene, 
etc.  J.  B.  Cohen,  "  Organic  Chemistry  for  Advanced 
Students,"  Pt.  II,  2d  Ed.  (1918),  369-75.) 

5.  For  what  is  benzidine  used  commercially?     Example. 

6.  Of  what  hydrocarbon  is  hydrazobenzene  a  derivative?   ben- 

zidine? 

169 


Experiment  No.  49 

DYES 

FORMATION  or  AN  Azo  DYE 
Preparation  of  Methyl  Orange 

NOTE 
Use  amounts  as  nearly  correct  as  possible. 

Make  ready  a  solution  of  i.o  gram  of  sodium  hydroxide  in 
10  cc.  of  water.  In  a  small  beaker,  No.  o,  dissolve  i.o  gram  of 
sulfanilic  acid  in  5  cc.  of  water  and  2.4  cc.  (i  mol.)  of  the  sodium 
hydroxide  solution.  Set  the  beaker  in  ice  and  diazotize  by  adding 
first  a  solution  of  0.42  gram  (i  mol.)  of  sodium  nitrite  (which 
should  be  powdered  to  make  it  dissolve  readily)  in  2  cc.  of  water, 
and  then  slowly,  with  stirring,  a  solution  of  0.5  cc.  (i  mol.)  of 
cone,  hydrochloric  acid  in  2  cc.  of  water.  A  reddish  solution  is 
often  obtained. 

In  a  separate  small  beaker  or  test-tube  mix  0.74  gram  (about 
20  drops  l)  (i  mol.)  of  dimethylaniline  and  0.37  gram  (about  13 
drops  l)  (i  mol.)  of  glacial  acetic  acid.  Add  this  solution  drop 
by  drop,  with  constant  stirring,  to  the  diazotized  solution. 
The  dye  begins  to  separate  at  once  and  forms  a  thick,  dark  red 
mass.  Treat  this  with  the  remaining  7.6  cc.  (3  mol.)  of  the 
sodium  hydroxide  solution  and  stir  well.  Filter  off  the  reddish- 
yellow  product  with  suction,  using  a  hardened  filter  paper2  or 
two  ordinary  filter  papers  in  the  bottom  of  the  funnel.  Re- 
crystallize  the  crude  methyl  orange  from  20  cc.  of  hot  water. 

1  From  the  lip  of  a  10  cc.  graduated  cylinder. 

2  A  hardened  filter  paper  is  one  which  has  been  treated  with  cone,  sulfuric  acid. 
It  is  tough  and  smooth  and  has  no  loose  fibres. 

170 


LABORATORY  EXPERIMENTS  171 

Leaflets  with  a  golden  luster  are  thus  obtained.     Allow  to  dry 
on  filter  papers.     Yield, -1.2  grams. 

NOTES 

Methyl  orange  is  the  sodium  salt  of  the  sulfonic  acid,  and  its 
aqueous  solution  has  a  yellow  color.  On  the  addition  of  an  acid  the 
free  sulfonic  acid  (Helianthine)  is  obtained,  which  has  a  red  color  in 
aqueous  solution.  The  use  of  the  dye  as  an  indicator  in  acidimetry 
and  alkalimetry  depends  upon  this  change  in  color.  (For  further 
discussion  of  this  color  change  see  Cohen,  "  Organic  Chemistry," 
Vol.  II  (1913),  p.' 380.) 

STUDIES  OF  TRIPHENYLMETHANE  DYES 
Phenolphthalein 

Mix  o.i  gram  of  phthalic  anhydride  and  o.i  gram  of  phenol 
in  a  test-tube,  and  add  2  drops  of  cone,  sulfuric  acid.  Heat 
gently  over  a  small  flame  with  constant  agitation  for  about  two 
minutes.  The  melt  will  become  dark  red  and  the  heating 
should  not  be  so  strong  that  the  material  blackens  on  account 
of  extensive  decomposition.  When  cold  treat  with  5  cc.  of 
water,  and  add  very  gradually  with  shaking  a  dilute  solution 
of  sodium  hydroxide  until  a  permanent  pink  color  is  obtained 
(no  more).  Dilute  a  portion  of  this  solution  and  test  the  suit- 
ability of  the  dissolved  phenolphthalein  as  an  indicator  by  adding 

first  a  trace  of  acid  and  then  a  trace  of  alkali.     (?) 

• 

Fluorescein 

Mix  o.i  gram  each  of  phthalic  anhydride  and  resorcinol  in 
a  test-tube  and  add  3-4  drops  of  cone,  sulfuric  acid.  Heat 
gently  for  two  minutes.  Allow  to  cool,  add  5  cc.  of  water, 
and  make  alkaline  with  sodium  hydroxide.  Transfer  a  drop  of 
this  solution  to  a  test-tube  full  of  water.  (?)  View  by  both 
reflected  and  transmitted  light. 

Crystal  Violet 

Place  o.i  gram  of  Michler's  ketone  (^/-tetramethyl-diamino- 
benzophenone) ,  5  drops  of  dimethylaniline,  and  2  drops  of 


172          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

phosphorus  oxychloride  in  a  test-tube,  and  heat  the  tube  in 
boiling  water  for  one-half  hour.     Add  10  cc.  of  water  and  stir. 

1.  Add  a  drop  of  liquid  to  about  20  cc.  of  water  and  note 
the  color. 

2.  Add  several  drops   to  20  cc.  of  water  and  treat  with  a 
little  ammonium  hydroxide  solution.     Let  stand  until  the  color 
has  disappeared  and  white  flocks  are  found  in  the  liquid  (several 
minutes).     Explain. 

To  a  portion  of  this  decolorized  solution,  add  very  dilute 
hydrochloric  acid  until  the  color  returns.  Explain. 

3.  To  a  second  dilute  portion  of  the  original   solution   add 
dilute  hydrochloric  acid.     What  makes  the  green  color  which 
changes  to  yellowish?     (See  E.  Q.  Adams  and  L.  Rosenstein, 
"The  Color  and  lonization  of  Crystal  Violet,"  Journ.  Amer. 
Chem.  Soc.,  36  (1914),  i452-73-) 

4.  To  a  third  dilute  portion  of  the  original  solution  add  a 
small  amount  of  zinc  dust  and  warm  for  a  few  minutes.     Why 
does  the  color  disappear? 

5.  Allow  the  remainder  of  the  original  solution  to  stand 
overnight  when  crystals  of  crystal  violet,  which  have  a  greenish 
luster,  will  separate  out  on  the  walls  of  the  test-tube. 

REFERENCES 

Holleman,  "Organic  Chemistry,"  4th  Ed.  (1914),  528. 

For  a  general  discussion  of  color  and  structure,  see  Curtiss, 
4 Relation  between  Color  and  Constitution,"  Journ.  Amer.  Chem. 
Soc.,  32  (1910),  795. 

QUESTIONS 

METHYL  ORANGE 

1.  What  is  diazotization? 

2.  What  is  the  diazo  structure?  the  diazonium  structure? 

3.  Write  the  structure  of  benzene  diazoic  acid;    of  benzene 

diazonium  hydroxide.     Why  are  these  formulas  assigned 
to  the  two  isomers? 

4.  Using  structural  formulas  and  equilibria  equations,  trace  the 

course  of  the  reaction  in  the  formation  of  an  arnino-azo 
dye  with  the  simplest  preparation  in  the  series,  ^-amino- 


LABORATORY  EXPERIMENTS  173 

azo-benzene  from  aniline  as  follows:  (i)  phenylammonium 
hydroxide  formed  when  aniline  is  dissolved  in  water, 
(2)  the  salt  formed  with  hydrochloric  acid  (this  is  partially 
hydrolyzed),  (3)  the  salt  (nitrite)  formed  when  nitrous 
acid  is  present,  (4)  the  amide  formed  from  this,  (5)  the 
tautomeric  change  to  the  diazoic  acid,  (6)  the  formation 
of  the  phenylammonium  salt  between  the  diazoic  acid 
and  a  second  molecule  of  pheny^ammonium  hydroxide 
(added  after  the  diazotization  is  complete),  (7)  the  com- 
pound formed  through  the  amide  formation  (azo-amino 
stage),  (8)  and  the  final  rearrangement  to  the  ^-amino- 
azo-benzene. 

5.  Follow  out  the  same  scheme  with  sulfanilic  acid  and  dimethyl 

aniline,  using  the  proper  modifications  due  to  the  presence 
of  the  sulfo  group. 

6.  Why  is  acetic  acid  used  in  the  second  part  of  the  experiment 

instead  of  hydrochloric?     Could  hydrochloric  be  used? 

7.  Why  is  sodium  hydroxide  added  at  the  end  of  the  reaction? 

8.  What   is   a   chromophore,    an   auxochrome   group?     Point 

out  any  such  groups  in  methyl  orange. 

*9.  Write  the  structure  of  methyl  orange  to  show  the  presence  of 
a  quinoid  nucleus,  and  also  the  changes  involved  in  its 
use  as  an  indicator.  (Cohen,  "  Organic  Chemistry," 
II  (1913),  380.) 

10.  What  is  the  leuco  base  of  an  azo  dye?     How  obtained? 

1 1 .  How  can  it  be  proved  that  in  the  making  of  methyl  orange  the 

coupling  has  taken  place  at  the  para  position  to  the 
dimethylamino  group? 

12.  How  is  the  coupling  carried  out  (in  acid,  neutral,  or  alkali 

solution)?     Why?     (Mohlau    and    Bucherer,    "Far 
chemisches  Praktikum,"  118.) 

13.  What  are  the  congo  dyes?     How  used  in  dyeing? 

*i4.  What  is  a  syn-diazo  compound,  and  an  anti-diazo  com: 

compound? 
*i5.  Which  one  enters  into  a  reaction?     (Holleman,  413,  417-9; 

Mohlau  and  Bucherer,  70.) 
*i6.  Why  should  the  diazotized  solution  not  stand  overnight 

before  coupling? 
*iy.  How  are  the  salts  of  the  anti-diazo  acid  obtained?    (Mohlau 

and  Bucherer,  71.)     Salts  of  the  diazonium  hydroxide  in 

solid  form?     Give  structures. 

1 8.  How  can  you  prepare  phenylhydrazine? 

19.  What  is  benzidine?     How  prepared?     For  what  used? 

20.  What  are  poly-azo  dyes?     How  prepared? 


174          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

*2i.  What  is  Bismarck  brown?     How  is  w-phenylenediamine 
hydrochloride  used  in  the  test  for  nitrites? 

PHENOLPHTHALEIN  AND  FLUORESCEIN 

22.  What  are  the  structural  formulas  of  phenolphthalein  and 

fluorescein? 

23.  What  are  some  of  the  derivatives  of  fluorescein? 

24.  What  is  the  theory  for  the  color  change  in  the  use  of  phenol- 

phthalein as  an  indicator? 

CRYSTAL  VIOLET 

25.  What  is  the  structural  formula  (quinoid)  for  crystal  violet? 

26.  Trace  the  course  of  the  reaction  beginning  with  the  addition 

product  formed  from  Michler's  ketone  and  dimethylanil- 
ine,  through  the  tautomeric  change  to  the  true  base,  and 
then  the  formation  of  the  dye  by  neutralization  with 
hydrochloric  acid. 

27.  Point  out  any  chromophore  and  auxochrome  groups  in  crys- 

tal violet. 

28.  What  is  the  parent  substance  of  the  fuchsine  series? 

29.  What  is  a  color  base?     Illustrate  in  the  case  of  crystal 

violet.     How  formed? 

30.  Explain  the  changes  that  take  place  in  the  presence  of  the 

alkali. 

31.  What  is  the  structure  of  the  leuco-base  of  crystal  violet? 

How  formed? 
*32.  What  happens  when  crystal  violet  is  treated  with   cone. 

hydrochloric  acid? 
3.  How  is  Michler's  ketone  manufactured? 

34.  Are  all  colored  substances  dyes? 

35.  What  is  a  mordant?     How  used? 

36.  What  is  a  lake? 

37.  What  is  a  vat  dye?     How  used?     Ex.  Indigo. 

38.  What  is  rosaniline,  fuchsine,  or  magenta?     Para-rosaniline? 

How  used  in  SchifT's  aldehyde  reagent? 
*3Q.  What  is  malachite  green?     How  prepared? 
*4O.  What  is  aurin?  rosolic  acid?     How  prepared? 
41.  What  is  indigo?     Summarize  the  steps  in  its  manufacture. 
*42.  What  is  alizarin? 
*43.  What    is    the    structure    of    indanthrene?     (Mohlau    and 

Bucherer,  225-6.) 

*  These  questions  are  not  required  for  study  in  the  "  short "  course. 


Experiment  No.  50 
FORMATION  OF  A  TRIPHENYLMETHANE  DYE 

Preparation  of  Crystal  Violet  from  Michler's  Ketone 
and  Dimethyl  Aniline 

Heat  a  mixture  of  6  cc.  of  dimethyl  aniline,  2.5  grams  of 

Michler's  ketone  (^X-tetramethyl-diamino-benzophenone),  an<^ 
2  cc.  of  phosphorus  oxychloride,  in  a  porcelain  evaporating  dish 
for  2\  hours  on  the  steam-bath.  Then  transfer  the  blue-colored 
mass  to  a  flask  with  water,  make  alkaline  with  a  solution  of 
sodium  hydroxide  (calculated  on  the  basis  of  the  amounts  of  the 
hydrolytic  products  of  the  phosphorus  oxychloride),  and  distill 
with  steam  (see  p.  158)  until  no  drops  of  the  unattacked  di- 
methylaniline  pass  over  (about  three  hours) .  After  the  addition 
of  the  sodium  hydroxide  the  blue  color  should  disappear  either 
on  standing  or  soon  after  the  distillation  is  begun,  and  a  reddish 
precipitate  formed.  If  it  does  not,  add  more  sodium  hydroxide. 
(Explain  the  color  change.)  After  cooling,  filter  the  reddish, 
solidified  color-base  remaining  in  the  distillation  flask  from  the, 
alkaline  solution,  wash  with  water,  and  boil  with  a  mixture 
250  cc.  of  water  and  2  cc.  of  cone,  hydrochloric  acid.  Filter  the 
blue  solution  while  hot  from  the  undissolved  color-base;  and 
boil  the  latter  again  with  a  fresh  quantity  of  the  dilute  hydro- 
chloric acid.  This  operation  should  be  repeated  until  the  sub- 
stance is  almost  entirely  dissolved.  On  cooling  and  standing, 
the  crystal  violet  separates  out  in  beautiful  needle  crystals  of  a 
greenish  color.  Filter  and  dry  in  the  air  on  filter  paper.  A 
further  quantity  may  be  obtained  by  adding  finely  pulverized 
salt  to  the  filtrate  ("  salting  out  ").  Yield,  about  4  grams. 

Make  a  dilute  solution  of  the  crystal  violet  and  perform 
experiments  2-4  given  under  crystal  violet  on  p.  172. 

175 


176          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 


QUESTIONS 

1.  What  is  a  "  condensing  "  agent? 

2.  \\toy  must  the  mixture  be  alkaline   before  distilling  with 

steam? 

3.  Why  must  dilute  hydrochloric  acid  be  used  for  preparing  the 

dye?     What  happens  when  stronger  acid  is  used? 
Answer  also  questions  25-43,  p.  174. 


Experiment  No.  51 

FORMATION  or  A  PHENOL  FROM  A  PRIMARY  AROMATIC  AMINE 
BY  MEANS  or  THE  DIAZO  REACTION 

Preparation  of  Phenol  from  Aniline 

Pour  10  cc.  of  cone,  sulfuric  acid  rapidly,  with  stirring, 
into  50  cc.  of  water,  and  to  the  hot  solution  slowly  add  10  cc.  of 
aniline,  with  constant  stirring  to  make  complete  solution.1 
(What  is  the  white  solid  first  formed?)  Transfer  to  a  liter  flask, 
then  add  200  cc.  of  water.  Diazotize  by  treating  the  cold  solu- 
tion with  the  calculated  amount  of  sodium  nitrite  (powdered  to 
make  it  dissolve  readily)  contained  in  about  40  cc.  of  water. 
Heat  on  the  steam-bath  for  thirty  minutes  at  a  temperature 
between  4o°-5o°,  with  the  thermometer  in  the  liquid.  (What  gas 
is  evolved?)  The  phenol  is  then  distilled  over  with  steam. 
(See  Aniline  Experiment,  p.  158.) 

Collect  about  600  cc.  of  distillate  (about  1.5-2  hours  are  re- 
quired). When  near  the  end  of  the  distillation  test  the  clear 
distillate  with  bromine  water  and  ferric  chloride,  according  to  the 
directions  given  below  in  c  and  d.  (?)  Compare  with  aniline, 
p.  1 60.  Saturate  this  distillate,  contained  in  a  liter  separatory 
funnel,  with  finely  powdered  sodium  chloride,  25  grams  for  every 
100  cc.  of  liquid,  and  extract  the  solution  three  times  with 
ether  (p.  74),  using  50  cc.  of  ether  for  the  first  extraction  and 
30  cc.  each  for  the  other  two. 

Filter  the  combined  ethereal  extracts  through  a  fluted 
filter2  to  remove  any  brownish  impurities  from  the  salt,  and 
then  dry  with  anhydrous  sodium  sulfate.  In  order  that  the 
small  amount  of  phenol  remaining  after  the  removal  of  the 

1  Any  precipitate  which  separates  on  cooling  will  dissolve  when  the  solution  is 
diluted. 

2  See  foot-note,  p.  128. 

177 


178          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

ether  may  be  left  in  a  small  flask  for  the  final  distillation,  the 
ether  is  distilled  over  in  the  manner  described  in  the  Aniline 
Experiment,  p.  161.  Distill  the  residue,  using  a  short  wide  tube 
or  an  adapter  as  an  air  condenser.  B.p.  183°,  m.p.  42.5°.  The 
specimen  should  be  white  and  should  solidify,  especially  when  the 
tube  is  placed  in  cold  water.  If  it  is  colored  re-distill  carefully. 
Yield,  8  grams. 

Reactions  of  Phenol  and  Derivatives 

a.  Test  the  reaction  of  an  aqueous  solution  of  phenol  with 
neutral  litmus  paper. 

b.  Add    a  little  sodium  hydroxide  solution  to   i   gram  of 
phenol.     Now  acidify  with  hydrochloric  acid.     Do  not  use  too 
much  water.    Any  change? 

c.  Dissolve  a  drop  of  phenol  in  water  and  add  bromine 
water  until  it  is  no  longer  absorbed.     Filter  off  the  precipitate 
and  wash  it  with  a  dilute  solution  of  sulfur  dioxide  or  of  sodium 
hydrogen  sulfite  until  there  is  a  strong  odor  of  sulfur  dioxide. 
Wash  with  water.     Dissolve  in  about  5  cc.  of  hot  alcohol,  filter, 
add  10  cc.  of  hot  water,  and  set  aside  to  crystallize.     Dry  it  on  a 
porous  tile  and  determine  its  melting-point.     For  what  is  this 
reaction  used?     Compare  with  the  action  of  bromine  and  of 
bromine  water  on  benzene  (p.  138),  and  on  amylene  (p.  45). 

NOTE 

The  sulphur  dioxide  converts  any  BraCeH^OBr  into  tribrom- 
phenol,  Br3C6H2OH. 

d.  To  a  dilute  solution  of  phenol  add  a  drop  of  ^  molar  ferric 
chloride  solution.     (?) 

e.  Add  a  drop  of  ferric  chloride  solution  to  dilute  solutions 
of  catechol,  resorcinol,  salicylic  acid  and  gallic  acid.     (?)     Com- 
pare the  structures  of  these  compounds. 

/.  Try  the  action  of  ferric  chloride  on  a  solution  containing 
a  drop  of  acetacetic  ester  and  on  another  containing  a  drop  of 
ace  ty  lace  tone.  Use  alcohol  in  each  case  to  make  the  solution 
homogeneous.  What  is  meant  by  the  enol  and  the  keto  form? 


LABORATORY  EXPERIMENTS  179 

To  which  one  is  this  color  reaction  supposed  to  be  due?    Do 

all  hydroxyl  compounds  give  color  reactions  with  ferric  chloride? 

Also   compare   the   action   of   ferric   chloride   on   aromatic 

amines  (aniline),  and  on  alpha-hydroxy  acids,  like  tartaric  acid. 

QUESTIONS 

1.  How  does  aniline  differ  from  ammonia?     Compare  the  action 

of  nitrous  acid  in  each  case. 

2.  Why  is  aniline  first  treated  with  sulfuric  acid? 

3.  What  compound  is  formed  when  aniline  and  sulfuric  acid 

react? 

4.  Would  there  be  any  objection  to  using  too  little  sodium 

nitrite?  too  much? 

5.  What  reason  is  there  for  heating  the  diazotized  solution? 

6.  Calculate  the  amount  of  sulphuric  acid  theoretically  neces- 

sary for  converting  10  grams  of  aniline  into  phenol,  and 
compare  with  the  amount  used. 

7.  Explain  the  principle  of  steam  distillation. 

8.  Why  is  steam  distillation  used  in  this  experiment? 

9.  How  can  you  tell  by  chemical  means  when  all  the  phenol 

has  been  distilled  over  with  steam? 

10.  Why  not  continue  the  steam  distillation  until  the  distillate 

gives  no  test  for  phenol? 

11.  Why  is  the  distillate  saturated  with  salt  before  extraction? 

12.  What  advantage  is  there  in  extracting  the  solution  three 

times  with  small  amounts  of  ether,  instead  of  once  with 

a  larger  amount  of  ether? 
;  13.  How  can  anhydrous  sodium  sulfate  be  used  as  a  drying 

agent? 
\  14.  Where  does  the  moisture  taken  up  by  the  sodium  sulfate 

come  from? 

^15.  Is  this  method  for  the  formation  of  phenols  practical? 
1 16.  Can  this  method  of  replacing  an  amino  group  with  hydroxyl 

be  used  in  the  case  of  aliphatic  amines? 
[17.  What  advantage  is  there  in  distilling  the  ether  from  a  small 

flask? 

18.  How  can  phenol  be  prepared  from  benzene  sulphonic  acid? 
i  19.  Compare  the  behavior  of  ethyl  alcohol  and  phenol  when 

treated  with  bromine. 

20.  Compare  the  action  of  the  halogens  and  of  nitric  acid  on 

phenol  and  on  benzene. 

21.  What  is  the  action  of  acetyl  chloride;  and  of  zinc  dust,  on 

phenol? 


Experiment  No.  52 

ALKYLATION  OF  AN  HYDROXYL  GROUP 

Preparation  of  Anisole  (Methyl-phenyl  Ether)  from  Phenol  and 
Dimethylsulfate 

Perform  this  experiment  with  apparatus  connected  with  the 
draft  pipe.  Dimethylsulfate  has  no  odor,  but  it  is  very  poison- 
ous to  some  people.  Be  careful  not  to  breathe  its  vapors  and 
since  it  is  readily  absorbed  do  not  allow  any  to  come  in  contact 
with  the  skin.  If  any  be  spilt  upon  the  clothes  these  should  be 
changed  immediately. 

Dissolve  12  grams  of  phenol1  in  a  solution  of  10  grams  of 
sodium  hydroxide  and  100  cc.  of  water.  Pour  this  into  a  250  cc. 
flask  and. add  slowly  and  with  continuous  shaking  25  grams  of 
dime  thy  Isulf  ate.2  Place  a  thermometer  in  the  mixture. 
There  is  a  slight  rise  in  temperature,  which  should  not  be 
allowed  to  exceed  40°  (cooling  is  usually  not  necessary).  The 
clear  liquid  becomes  turbid  and  in  a  few  minutes  a  layer  of  oil 
will  float  on  the  surface.  The  reaction  may  be  considered  com- 
plete when  the  temperature  no  longer  rises  and  the  products 
cool. 

To  destroy  the  excess  of  dimethylsulfate  (dry  the  flask  if 
it  has  been  placed  in  water),  attach  an  upright  air  condenser, 
and  heat  the  mixture  to  the  boiling-point  with  frequent  shaking. 
(How  does  this  destroy  the  dimethylsulfate?)  Finally,  cool 
the  liquid,  add  a  solution  of  6  grams  of  sodium  hydroxide  in  60 

1  Melt  it  by  placing  the  bottle  in  warm  water.     If  phenol  should  come  in  con- 
tact with  the  skin  use  dilute  alcohol  immediately. 

2  Opening  sealed  bottles:    Wrap  the  bottle  in  a  towel,  leaving  the  narrow 
sealed  end  protruding,  and  make  a  file  mark  around  the  tube  near  the  end.     Hold 
it  over  a  beaker  in  a  slanting  po?ition  and  knock  off  the  end  with  a  sharp  blow  of 
the  file,  or  touch  the  mark  with  the  hot  fused  end  of  a  glass  rod. 

180 


LABORATORY  EXPERIMENTS  181 

cc.  of  water,  and  extract  once  with  ether.  The  liquid  must  be 
alkaline  when  the  extraction  is  made.  It  cannot  be  tested 
directly  since  the  oil  would  prevent  the  litmus  paper  from  ab- 
sorbing water  and  indicating.  Test  a  drop  drawn  off  from  the 
liquid  in  the  separatory  funnel.  Dry  the  ethereal  solution  with 
calcium  chloride.  Remove  the  ether  by  distillation,  observing 
the  ordinary  precautions  (see  p.  70),  and  then  distill  the  anisole. 
The  boiling-point  of  anisole  is  153.9°  cor-  The  yield  amounts 
to  about  95  per  cent  of  the  theory. 

QUESTIONS 

1.  Write  all  the  reactions  involved  in  the  formation  of  anisole 

from  phenol,  upon  the  assumption  that  an  "  oxonium  " 
compound  is  formed  as  an  intermediate  product. 

2.  How  is  dime  thy  Isulf  ate  prepared? 

3.  What  advantages  has  it  over  methyl  iodide  as  a  methyl- 

ating  agent?  over  diazomethane? 

4.  Why  is  the  sodium  hydroxide  used? 

5.  Why  must  the  temperature  of  the  mixture  be  kept  under  40°? 

6.  Would  an  excess  of  dime  thy  Isulf  ate  be  likely  to  affect  the 

yield  of  anisole? 

7.  To  what  class  of  organic  compounds  does  anisole  belong? 

dimethylsulfate? 

8.  Could  dimethylsulfate  be  used  for  alky  la  ting  the  hydroxyl 

group  in  water,  ethyl  alcohol,  and  acetic  acid?     Equations. 

9.  Does  it  make  any  difference  as  to  the  order  in  which  the 

dimethylsulfate,  phenol,  and  sodium  hydroxide  are 
mixed? 

10.  Why  is  the  anisole  mixture  made  slightly  alkaline  before 

extracting  with  ether? 

11.  Could  anhydrous  sodium  sulfate  be  used  in  place  of  calcium 

chloride  for  drying  the  ethereal  solution  of  anisole? 

12.  How  can  anisole  be  changed  into  phenol? 

13.  What  is  the  Zeisel  method  of  estimating  methoxy  groups  in 

alkaloids,  etc.? 

14.  Could  dimethylsulfate  be  used  for  methylating  amino-  and 

imino-groups?     Examples. 

15.  How  can  pure  mono-methyl  aniline  be  prepared? 

16.  What  is  the  action,  if  any,  of  bromine,  cone,  nitric  acid, 

cone,  sulfuric  acid,  cone,  sodium  hydroxide,  potassium 
permanganate,  and  alcoholic  potassium  hydroxide  at  a 
high  temperature,  on  anisole? 


Experiment  No.  53 
BENZALDEHYDE 

Perform  the  following  reactions: 

1.  Silver-mirror   test.     Make    an    ammoniacal    solution    of 
silver  nitrate,  as  given  under  Acetaldehyde,  p.  91,  and  add  a  drop 
of  sodium  hydroxide  solution.     If  a  precipitate  forms  dissolve  it 
with  a  little  more  ammonium  hydroxide.     Add  a  single  drop 
(or  a  lesser  amount)    of  benzaldehyde,  shake,  and  let  stand. 
The  mirror  forms  very  slowly. 

2.  Try  the  action  of  the  fuchsine-sulfurous  acid  reagent 
(Schiffs   aldehyde   reagent)    p.  92,  on  benzaldehyde.     If  the 
drop  of  benzaldehyde  is  run  down  the  side  of  the  test-tube  it 
will  float  on  the  surface  of  the  solution  and  will  assume  the 
color  of  the  fuchsine  without  coloring  the  entire  solution. 

3.  Does  benzaldehyde  reduce  Fehling's  solution?    Try  it. 

4.  Add  several  drops  of  benzaldehyde  to  2  or  3  cc.  of  a 
saturated  solution  of  sodium  bisulfite,  and  shake  vigorously. 
Of  what  do  the  white  crystals  consist?    Filter  with  suction  and 
then  warm  with  a  solution  of  sodium  carbonate.     (?) 

5.  Add  a  drop  of  benzaldehyde  to  a  solution  of  a  drop  of 
phenylhydrazine  in  3  cc.  of  dilute  acetic  acid  (i  :  i).  What  is  the 
yellow  precipitate? 

6.  Rub  a  drop  of  benzaldehyde  on  a  watch  glass.    What  are 
the  crystals  that  form  after  a  short  time? 

7.  Make  a  very  dilute  solution  of  soluble  starch  and  add  to 
it  a  few  drops  of  dilute  potassium  iodide  solution.    Spread  a 
drop  of  benzaldehyde  on  a  watch  glass  with  the  aid  of  a  stirring- 
rod.    Allow  it  to  remain  for  a  minute  or  two,  and  then  add  a 
few  drops  of  the  starch-potassium  iodide  solution.      Set  the 
watch  glass  over  a  filter  paper,  and  stir  with  the  rod.     Explain 
the  formation  of  the  blue  color  (see  Question  9  below). 

Which  of   the   above  reactions   are   also   characteristic  of 
ketones? 

182 


LABORATORY  EXPERIMENTS  183 

8.  In  a  test-tube  thoroughly  mix  about  o.i  gram  of  cin- 
namic  acid  and  about  5  cc.  of  a  cold  strong  solution  of  potassium 
permanganate.  Note  the  odor.  Explain. 

What  type  of  unsaturated  aromatic  compounds,  with  relation 
to  the  position  of  the  double  bond,  undergo  this  reaction? 

Outline  the  commercial  preparation  of  vanillin  from  eugenol 
and  of  piperonal  from  safrol.  (Holleman,  "  Organic  Chemistry," 
4th  Ed.  (1914),  482-5;  Stoddard,  "Introduction  to  Organic 
Chemistry,'7  2d  Ed.  (1918),  347,  342.) 

QUESTIONS 

1.  Does  benzaldehyde  react  with  Fehling's  solution? 

2.  Write  equations  and  complete  structures  involved  in  the 

reactions  between  benzaldehyde  and  sodium  hydrogen 
sulfite,  and  between  the  product  and  sodium  carbonate. 

3.  Could  a  dilute  solution  of  acid  sodium  sulfite  be  used  instead 

of  the  concentrated? 

4.  Could  any  other  reagent  be  used  in  place  of  the  sodium  car- 

bonate? 

5.  Write  equations  and  structures  for  the  reaction  with  phenyl- 

hydrazine. 

6.  Could  50  per  cent  hydrochloric  acid  be  used  in  place  of 

the  50  per  cent  acetic  acid? 

7.  Could   phenylhydrazine    hydrochloride    be    used?      What 

modification  is  generally  necessary? 

8.  Could  hydrazine  itself  be   used?    *Semicarbazide?     (Per- 

kin  and  Kipping,  "  Organic  Chemistry,"  New  Ed., 
(1911),  456. 

9.  What  happens  when  benzaldehyde  is  exposed  to  the  air? 

(For  discussion  of  autoxidation,  see  Holleman,  "  Organic 
Chemistry,"  4th  Ed.  (1914),  428;  and  Bayliss,  "  Principles 
of  General  Physiology"  (1915),  580.) 

10.  Explain  what  takes  place  in  the  experiment  with  starch  and 

potassium  iodide. 

11.  Write  equations  for  the  reactions  occurring  when  benzalde- 

hyde is  treated  with  the  following  reagents:  (a)  phos- 
phorus pentachloride,  (b)  mixture  of  nitric  and  sulfuric 
acids  at  o°,  (c)  hydroxylamine  hydrochloride  and  sodium 
carbonate,  *(d)  acetone  and  sodium  hydroxide  solution 
(compare  Perkin  and  Kipping,  456),  *(e)  alcoholic  solu- 
tion of  potassium  cyanide,  *(/)  ammonia,  (g)  aniline. 
*  These  questions  are  not  required  for  study  in  the  "  short  "  course. 


Experiment  No.  54 
ADDITION  OF  HYDROGEN  TO  AN  ETHYLENE  DERIVATIVE 

Preparation    of    Hydrocinnamic    Acid    (Phenylpropionic    Acid) 
from  Cinnamic  Acid 

The  3  per  cent  sodium  amalgam  used  in  this  experiment  is 
prepared  as  follows:  Weigh  out  in  a  dry  evaporating  dish  or 
casserole  145  grams  of  pure  dry  mercury.  Warm  on  the  steam- 
bath  to  75°.  Prepare  4.5  grams  of  sodium,  free  from  crust  and 
from  the  liquid  which  can  be  removed  with  filter  paper.  Cut  off 
slices  and  immediately  press  them  to  the  bottom  of  the  warm 
mercury  in  rather  rapid  succession  by  means  of  a  short  moderately 
thick  glass  rod,  drawn  out  to  a  point  and  bent  at  a  short  right 
angle.  Use  a  pestle  if  necessary  in  the  above  operation.  After 
each  piece  is  added  a  somewhat  violent  reaction  takes  place.  If 
the  operation  is  conducted  quickly  all  the  sodium  can  be  added 
before  the  mass  solidifies.  This  operation  must  be  carried  out 
under  the  hood,  using  the  glass  door  as  a  shield;  protect  the  eyes 
with  goggles  and  the  hands  with  gloves.  These  precautions  are  ab- 
solutely necessary  because  pieces  of  burning  sodium  are  often  pro- 
jected in  different  directions  from  the  dish.  Break  up  the  semi- 
solid  amalgam  at  once  and  transfer  it  to  a  tightly  stoppered 
dry  bottle. 

Into  a  250  cc.  flask  put  5  grams  of  cinnamic  acid,  80  cc.  of 
water  containing  1.4  grams  of  sodium  hydroxide,  and  150  grams 
of  sodium  amalgam  (3  per  cent)  in  small  portions.  Shake  the 
mixture  well  after  each  addition.  At  the  beginning  the  amalgam 
liquefies  rapidly,  very  little  hydrogen  is  evolved  and  the  solution 
becomes  warm.  Toward  the  end  the  amalgam  does  not  liquefy 
at  all  readily  and  numerous  bubbles  of  hydrogen  are  evolved. 
Add  more  water,  if  necessary,  to  dissolve  any  precipitate.  (?) 

184 


LABORATORY  EXPERIMENTS  185 

Take  out  a  few  drops  of  the  solution,  dilute,  acidify  with  dilute 
hydrochloric  acid,  neutralize  with  and  add  a  slight  excess  of 
sodium  carbonate  and  then  a  drop  of  a  very  dilute  solution  of 
potassium  permanganate.  If  the  permanganate  is  decolorized 
or  turns  brown  at  once,  cinnamic  acid  is  still  present  and  the  solu- 
tion must  be  warmed  on  the  steam-bath,  shaken  occasionally, 
and,  if  necessary,  more  amalgam  added  till  the  solution  no  longer 
decolorizes  permanganate.  This  permanganate  test  is  of  great 
value  for  the  detection  of  unsaturated  compounds.  (Compare 
test  for  " double  bond,"  p.  44-5.)  The  test  cannot  be  applied  to 
the  solution  when  there  is  fixed  alkali  in  excess  because  it  is  some- 
times masked  by  the  formation  of  a  green  manganate. 

When  the  reduction  is  complete,  pour  off  from  the  mercury, 
filter  and  then  precipitate  the  hydrocinnamic  acid  by  adding 
1 8  cc.  of  concentrated  hydrochloric  acid,  or  more,  depending 
on  the  amount  of  amalgam  used.  The  product  usually  separates 
as  an  oil  which  crystallizes  when  the  solution  is  cooled  and 
stirred.  Filter  off,  test  the  filtrate  for  more  of  the  product  by 
adding  dil.  hydrochloric  acid  and  allowing  to  stand,  and  re- 
crystallize  from  about  200  cc.  of  hot  water.  Yield,  4.5  grams. 

Hydrocinnamic  acid  crystallizes  in  long  colorless  needles  which 
melt  at  49°.  It  boils  at  280°.  It  is  easily  soluble  in  boiling 
water,  in  alcohol,  and  in  ether.  It  is  volatile  with  water  vapor, 
and  solutions  of  it  cannot  be  concentrated  by  boiling  without 
loss.  It  is  soluble  i  part  in  168  parts  of  water  at  20°. 

The  reduction  of  an  unsaturated  acid  by  sodium  amalgam 
can  only  be  carried  out,  apparently,  when  the  double  bond  is 
adjacent  to  the  carboxyl.  When  the  double  bond  is  further  re- 
moved the  reduction  may  often  be  carried  out  by  first  adding 
hydriodic  acid  and  then  reducing  with  zinc  dust  or  the  zinc- 
copper  couple  in  an  alcoholic  solution  and  in  presence  of  a 
little  dilute  acid.  The  reduction  may  also  be  effected  electrolyt- 
ically. 

NOTE 

The  German  name  for  cinnamic  acid  is  Zimmtsaure,  and  of 
hydrocinnamic  acid,  Hydrozimmtsaure. 


186          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

QUESTIONS 

1.  What  is  cinnamic  acid? 

2.  How  is  cinnamic  acid  prepared?     (Perkin's  reaction.) 

3.  Explain  why  the  amalgam  is  used  instead  of  metallic  sodium. 

4.  Point  out  what  is  oxidized  and  what  is  reduced. 

5.  What  is  the  white  precipitate  that  sometimes  forms  toward 

the  end  of  the  reduction?     Explain  its  formation. 

6.  In  the  test  for  unat tacked  cinnamic  acid,  explain  why  the 

solution  must  first  be  acidified  with  hydrochloric  acid  and 
then  made  alkaline  with  sodium  carbonate.  How  else 
could  the  same  condition  be  obtained?  What  effect  would 
the  sodium  hydroxide  have  on  the  test? 

7.  Could   the   following  compound  be   reduced  with  sodium 

amalgam  in  water:    C6H5-CH  :  CH-CH2COOH? 

8.  How  does  sodium  amalgam  react  in  an  ethyl  alcohol  solution? 

Give  an  example.  (Perkin  and  Kipping,  "Organic, 
Chemistry,"  New  Ed.  (1911),  385-6,  628.)  When  is  amyl' 
alcohol  used?  What  advantage  is  there  in  using  alcohol? 

9.  What  other  reducing  agents  are  used  for  reducing  the  olefine 

bond? 

10.  How  can  benzene  be  reduced    to    cyclohexane?     (Perkin 

and  Kipping,  365,  623.) 

11.  Discuss  the  hydrogenation  (reduction)  of  oils.     See  C.  A. 

Ellis,  Journ.  Industrial  and  Eng.  Chem.,  5  (1913),  95-106; 
and  his  book,  "  The  Hydrogenation  of  Oils,"  published  by 
Van  Nostrand, 


Experiment  No.  65 

REPLACEMENT  OF  A  DIAZO- GROUP  BY  CYANOGEN  (SANDMEYER 

REACTION) 

Preparation  of  ^-Tolunitrile  (^-Tolylcyanide)  from  />-Toluidine 

Perform  all  the  operations  under  the  hood.  Dissolve  1 2  grams 
of  powdered  copper  sulfate  crystals  in  50  cc.  of  water  in  a  500  cc. 
flask  by  heating  on  the  steam-bath;  then  add  gradually,  with 
continuous  heating,  a  solution  of  14  grams  of  powdered  potassium 
cyanide  in  25  cc.  of  water.  Since  cyanogen  is  evoked  the  greatest 
care  must  be  taken  not  to  breathe  the  vapors. 

While  the  potassium  cuprous  cyanide  solution  is  further 
gently  heated  on  the  steam-bath,  prepare  the  toluene  diazonium 
chloride  solution  as  follows:  Warm  5  grams  of  ^-toluidine  with 
a  mixture  of  10  cc.  of  concentrated  hydrochloric  acid  and  25  cc. 
of  water  until  solution  takes  place.  Then  set  the  beaker  in 
ice  and  stir  in  order  that  the  toluidine  hydrochloride  may 
separate  out  in  as  small  crystals  as  possible.  To  this  ice- 
cooled  mixture  add  gradually  with  good  stirring  a  solution  of 
4  grams  of  powdered  sodium  nitrite  (more  than  i  molecular 
equivalent)  in  15  cc.  of  water  until  a  drop  of  the  reaction 
mixture  gives  a  permanent  blue  color  with  starch-iodide  l  paper, 
or  until  you  just  notice  the  odor  of  the  oxides  of  nitrogen  from  the 
excess  of  nitrous  acid.  The  temperature  of  the  mixture  should 
not  rise  above  o°  at  any  time.  Pour  this  diazotized  solution, 
in  small  portions  during  ten  minutes,  into  the  hot  cuprous  cyanide 
solution,  with  frequent  shaking.  A  rapid  effervescence  occurs, 
nitrogen  and  some  hydrocyanic  acid  being  evolved.  Heat  for 
about  a  quarter  of  an  hour  on  the  steam-bath.  Then  distill  over 
the  tolunitrile  with  steam  (see  p.  158).  If  the  solid  separates 
in  the  condenser  tube  shut  off  the  water,  and  after  the  material 

1  Prepared  by  soaking  strips  of  filter  paper  in  a  very  dilute  solution  of  starch 
and  potassium  iodide.  The  papers  are  dried  and  kept  in  a  closed  bottle. 

187 


188          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

melts  and  flows  through,  slowly  turn  on  the  water  again.  This, 
operation  must  also  be  carried  out  under  a  hood  with  a  good 
draft,  as  not  only  is  hydrocyanic  acid  liberated,  but  a  small 
quantity  of  the  isonitrile  which  is  formed  in  the  reaction  pro- 
duces a  disagreeable  odor.  Continue  the  distillation  until  no 
more  of  the  oil  passes  over.1  The  nitrile  solidifies  in  the  receiver 
on  cooling  as  a  yellow  crystalline  mass.  Cool  thoroughly, 
decant  off  the  water,  and  press  out  the  substance  on  a  porous 
tile.  Distill  the  product  from  a  small  flask,  using  a  short  tube 
as  an  air  condenser.  Best  results  are  obtained  by  distilling  the 
nitrile  in  vacua  (p.  76).  If  the  oil  does  not  solidify,  extract 
with  ether,  shake  the  ethereal  solution  with  sodium  hydroxide 
solution  to  remove  the  cresol  (?),  and  then  after  separating  and 
drying  with  anhydrous  sodium  sulfate  and  evaporating  the 
ether  in  a  small  flask  as  in  the  Aniline  Experiment  (p.  161),  dis- 
till the  residue  directly.  Boiling-point,  218°  at  760  mm.  and 
about  103°  at  21  mm.,  melting-point,  29°.  Yield,  3.7  grams. 

QUESTIONS 

1.  Give  equations  to  show  the  formation  of  the  cuprous  cyanide, 

and  of  the  nitrile. 

2.  Why  is  it  advantageous  to  have  the  toluidine  hydrochloride 

separate  in  small  crystals? 

3.  Why  is  the  solution  kept  cold  during  the  diazotization? 

4.  Explain  the  starch-iodide  test  for  free  nitrous  acid. 

5.  What  is  the  formula  for  the  isonitrile? 

6.  How  can  you  account  for  the  presence  of  any  cresol? 

7.  How  is  the  cresol  removed? 

8.  What  is  the  Gattermann  modification   of  the   Sandmeyer 

reaction? 

9.  What  other  derivatives  can  be  prepared  by  means  of  the 

Sandmeyer  reaction? 

10.  Is  it  necessary  to  use  cuprous  iodide  in  order  to  prepare 

phenyl  iodide  from  aniline? 

11.  How    is    the    ^-tolunitrile    converted   into   ^-toluic   acid? 

Give  the  "  steps  "  in  this  reaction. 

12.  How  can  you  prepare  aceto-nitrile  (methyl  cyanide)  from 

acetamide?  from  methyl  iodide? 

13.  What  is  the  action  of  sodium  and  alcohol  on  a  nitrile? 

1  The  residue  in  the  flask  should  not  be  emptied  where  acid  might  be  added 
and  thus  cause  evolution  of  HCN. 


Experiment  No.  56 

OXIDATION  WITH  POTASSIUM  PERMANGANATE  IN  A  NEUTRAL 

SOLUTION 

Preparation  of  Acetanthranilic  Acid  (0-Acetamiao-benzoic  Acid) 
from  Acet-0-toluidide 

In  a  500  cc.  flask  dissolve  8  grams  of  potassium  permanganate 
and  6  grams  of  magnesium  sulfate  crystals  in  250  cc.  of  water. 
Add  3  grams  of  acet-0-toluidide  (Expt.46,p.  164), connect  the  flask 
to  an  upright  condenser  and  heat  slowly  to  boiling.  Continue 
the  boiling  with  a  low  flame  and  shake  frequently  until  all  the 
permanganate  has  been  used  up  (1-1.5  hours x).  Test  by 
filtering  a  few  cc.  (?)  Filter  the  hot  solution  (it  niters  more 
rapidly  when  hot)  of  potassium  acetanthranilate  from  the 
brown  precipitate  (?)  with  suction  in  a  lo-cm.  Buchner  funnel, 
using  two  filter  papers.  If  the  filtrate  begins  to  boil  under  the 
diminished  pressure,  allow  air  to  enter  by  squeezing  the  rubber 
tube  over  the  outlet  of  the  suction  flask  until  a  small  opening  is 
made  momentarily.  The  filtrate  will  probably  be  colored  at 
first  with  the  fine  brown  particles.  As  soon  as  it  comes  through 
water-white  and  clear  remove  the  tube  and  transfer  the  brown 
liquid  in  the  filtering  flask  to  the  flask  containing  the  main 
bulk  of  the  solution,  then  continue  the  filtration.  If  necessary, 
filter  again,  by  gravity.  What  is  the  reaction  of  the  filtrate 
with  neutral  litmus?  Then  carefully  add  to  the  clear  colorless 
filtrate  with  stirring  the  calculated  amount  of  sulfuric  acid  (as 
approximately  normal  solution)  based  upon  the  theoretical  yield, 
to  set  free  the  acetanthranilic  acid.  Let  stand  until  cold. 

1  If  the  permanganate  has  not  all  disappeared  in  this  time  the  little  that  remains 
can  be  destroyed  by  adding  in  very  small  amounts  through  the  top  of  the  condenser 
i  or  2  cc.  of  alcohol,  or  a  little  sulfurous  acid  or  a  sulfite.  (Explain  the  action.) 

189 


190          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

Filter  off  with  suction  the  acetanthranilic  acid,  which  is  precipi- 
tated as  fine  white  needle  crystals,  and  wash  with  a  little  cold 
water.  Test  the  filtrate  for  complete  precipitation  by  adding 
more  sulfuric  acid.  Melting-point,  185°.  Yield,  75  per  cent 
of  the  theory. 

NOTE 

The  brown  stains  can  easily  be  removed  from  the  hands  and 
apparatus  by  means  of  a  solution  of  sodium  bisulfite. 

QUESTIONS 

i.  What  is  the  specific  object  of  the  magnesium  sulfate? 
2.*  Why  is  it  necessary  that  this  object  be  attained? 

3.  What  becomes  of  the  potassium  and  of  the  manganese  of 

the  potassium  permanganate  during  the  oxidation? 

4.  How  can  anthranilic  acid  be  prepared  from  acetanthranilic 

acid? 

5.  Why  cannot  anthranilic  acid  be  formed  by  the  direct  oxida- 

tion of  0-toluidine? 

6.  What  is  meant  by  "  blocking  "  or  "  protecting  "  the  amino 

group? 

7.  How  can  anthranilic  acid  be  obtained  from  its  potassium 

salt? 

8.  What  is  the  best  method  for  purifying  anthranilic  acid? 

(Same  as  used  for  any  amino  acid.) 

9.  How  is  anthranilic  acid  obtained  from  phthalic  acid?     Where 

is  this  reaction  used  commercially? 

10.  What  is  the  effect  of  hydrochloric  acid  on  anthranilic  acid? 
Is  the  product  soluble  in  water? 


Experiment  No.  57 

FORMATION  or  AN  AROMATIC  ESTER  FROM  THE  ACID  AND  THE 

ALCOHOL l 

Preparation  of  Methyl  Salicylate   (Oil  of  Wintergreen)  from 
Salicylic  Acid  and  Methyl  Alcohol 

Place  17  grams  of  salicylic  acid  in  a  125  cc.  round-bottomed 
flask,  add  30  cc.  of  methyl  alcohol  and  then  gradually  and  with 
shaking,  add  4.5  cc.  of  cone,  sulfuric  acid.  Add  a  few  pieces  of 
porous  tiling,  connect  with  an  upright  or  reflux  condenser,  and 
heat  on  a  steam-bath  for  about  2.5  hours.  When  the  reaction  has 
proceeded  for  some  time  the  oil  of  wintergreen  formed  stays 
at  the  bottom  of  the  flask  and  sometimes  when  stirred  by  the 
boiling  and  dripping  from  the  condenser  forms  an  emulsion 
which  resembles  a  precipitate.  Distill  off  the  methyl  alcohol 
over  the  steam-bath  in  the  regular  manner,  transfer  the  residue 
to  a  separatory  funnel,  add  about  40  cc.  of  water,  shake,  separate 
the  lower  layer  which  is  the  methyl  salicylate,  and  wash  it  in  the 
separatory  funnel  first  with  water,  then  with  dilute  sodium 
carbonate  solution  (Why?)  and  finally  with  distilled  water. 
Separate  from  the  water,  dry  over  anhydrous  sodium  sulfate, 
and  purify  by  distillation  under  diminished  pressure  (p.  76). 
If  an  emulsion  is  formed  in  the  washing,  allow  to  stand  thirty 
minutes,  and  if  it  does  not  subside,  separate  the  layers  as  well  as 
possible,  and  then  dry  over  anhydrous  sodium  sulfate.  The 
turbid  water  layer  contains  only  a  very  small  amount  of  product. 

All  the  ester  distills  at  constant  temperature  provided  the 
pressure  remains  constant.  The  boiling-po'nt  of  methyl  salicy- 
late is  224°  at  760  mm.,  and  115°  (approx.)  at  20  mm.  Its  specific 
gravity  is  1.197  at  °°-  Yield,  17  grams. 

1  Compare  ethyl  acetate,  p.  106. 
191 


192          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

QUESTIONS 

1.  Define  an  ester. 

2.  Why  not  use  the  term  "  ethereal  salt  "? 

3.  What  is  the  structure  of  salicylic  acid? 

4.  Explain  why  cone,  sulfuric  acid  is  used. 

5.  Could  dilute  sulfuric  acid  be  used? 

6.  Could  cone,  hydrochloric  acid  be  used? 

7.  Why  is  not  methyl  sulfate  formed  instead  of  methyl  salicylate 

in  the  experiment? 

8.  What  effect  has  an  excess  of  methyl  alcohol  on  the  yield  of 

methyl  salicylate?  an  excess  of  salicylic  acid? 

9.  Calculate  the  theoretical  amounts  and  compare  with  the 

amounts  used. 

10.  Would  there  be  any  methyl  salicylate  formed  if  the  alcohol 

and  acid  were  heated  alone? 

11.  Why  must  the  methyl  alcohol  be  removed  before  the  mixture 

is  poured  into  water? 

12.  Why  is  sodium  carbonate  used  in   the  washing?     Could 

sodium  hydroxide  be  used?     Why? 

13.  Can  you  suggest  any  other  drying  agents  that  could  be  used 

instead  of  anhydrous  sodium  sulfate? 

14.  What  is  E.  Fischer's  method  of  esterification? 

15.  How  is  Fischer's  method  used  in  the  analysis  of  proteins? 

(Perkin   and   Kipping,  "  Organic  Chemistry,"  New  Ed., 
(1911),  554). 

1 6.  Outline  three  other  methods  of  preparing  esters. 

17.  Compare  the  physical  properties  of  acids  and  their  esters 

(boiling-point,  solubility,  conductivity,  etc.). 

18.  Show  by  means  of  structural  formulas  the  difference  between 

the  methyl  ether  of  salicylic  acid  (methyl  salicylic  acid) 
and  the  methyl  ester  of  salicylic  acid  (methyl  salicylate). 

19.  How  could  you  differentiate  chemically  between  the  two 

compounds  in  No.  18? 

20.  How  could  you  separate  by  chemical  means  salicylic  acid 

and  methyl  salicylate? 

21.  How  is  salicylic  acid  prepared  commercially? 

22.  Discuss  the  chemical  combination  of  oil  of  wintergreen  as 

found  in  nature. 


Experiment  No.  58 
Tannin  (Tannic  Acid) 

Make  up  25  cc.  of  an  approximately  i  per  cent  solution  of 
tannin1  for  the  first  three  experiments: 

1.  Add  a  few  drops  of  ^  molar  ferric  chloride  solution  to  about 
5  cc.  of  the  solution  of  tannin.     (?)     Dilute  i  cc.  of  the  original 
solution  of  tannin  to  50  cc.  and  add  a  drop  of  the  ferric  chloride 
solution.     (?)     Repeat,  using  gallic  acid.     (?)     Compare  with 
section  e  under  Phenol  Experiment  (p.  178). 

2.  Add  to  the  dilute  solution  of  tannin  a  normal  solution  of 
lead  acetate.     Repeat,  using  copper  sulfate.     Results? 

3.  Dissolve  about  o.i  gram  of  gelatin  in  10  cc.  of  warm  water, 
cool,  and  add  some  of  the  dilute  i  per  cent  solution  of  tannin. 

4.  Ink.    Dissolve  i  gram  of  tannin  in  10  cc.  of  hot  water, 
0.5  gram  ferrous  sulfate  in  5  cc.  of  hot  water,  and  0.05  gram  of 
gum  arabic  in  5  cc.  of  hot  water.     Cool  the  solutions  and  mix 
them.     Write  on  a  piece  of  paper  with  some  of  the  ink,  using  a 
new  pen.     Add  a  few  drops  of  ferric  chloride  to  a  little  of  the 
ink  and  write  with  the  mixture.     Compare  the  results  in  the 
two  cases  and  explain.     Put  the  paper  away  and  examine  the 
writing  with  the  two  samples  of  ink  at  the  next  exercise.     Ex- 
plain. 

NOTE 

The  ferrous  sulfate  snould  contain  no  ferric  sulfate.  Use  the  pure 
greenish  solid.  If  it  is  colored  yellow  or  brown  it  has  been  oxidized 
in  the  air  and  is  worthless. 

REFERENCE 

Holleman,  "  Organic  Chemistry,"  4th  Ed.  (1914),  473. 
1  This  solution  must  be  freshly  prepared,  since  it  slowly  decomposes  on  standing. 

193 


194          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

QUESTIONS 

1.  Where  is  tannin  obtained? 

2.  Is  tannin  a  true  organic  (carboxylic)  acid? 

3.  What  is  Fischer's  proposed  formula  for  tannin?     (For  an 

extended  discussion  of  the  subject,  see  Emil  Fischer, 
"  Synthesis  of  Depsides;  Lichen-substances  and  Tannin," 
Journ.  Amer.  Chem.  Soc.,  36  (1914),  1170.  For  formula, 
read  pp.  1193-4.) 

4.  With  lead  acetate,  does  tannin  precipitate  lead  tannate  or 

a  complex  of  lead  acetate  and  tannin? 

5.  Compare  the  reaction  with  gelatine  to  the  use  of  tannin  in 

tanning  hides.     Also  with  the  reaction  of  milk  in  tea. 

6.  Why  is  gum  arabic  used  in  the  ink? 

7.  What  changes  take  place  in  the  ink  on  the  paper  after 

standing? 

8.  In  commercial  ink  how  is  the  ferrous  salt  kept  from  oxidation? 

9.  As  far  as  you  can,  show  how  the  "  depsides"  are  synthesized. 

(See  Fischer's  article  above.) 
10.  How  is  tannin  used  in  dyeing? 


Experiment  No.  59 

ADDITION  or  A  HALOGEN  ACID  TO  AN  OLEFINE 

Preparation  of  Trans- 1,8-Dichlor-terpane  (d-Limonene- 
dihydrochloride)  from  d-Limonene 

To  a  50  cc.  distilling-flask  with  an  air  condenser  attached  add 
20  cc.  of  crude  d-limonene  1  and  a  small  amount  of  bright  sodium. 
Distill  and  collect  separately  the  fraction  between  170°-!  76°. 
Redistill  this  fraction,  using  another  small  piece  of  clean  sodium, 
and  collect  the  portion  boiling  close  to  the  boiling-point  of  pure 
J-limonene,  175°  (uncor.).  It  is  necessary  to  use  pure  d-limonene 
in  the  experiment.  Destroy  the  sodium  in  the  residues  by  treat- 
ment with  alcohol  before  the  apparatus  is  cleaned  with  water. 

Arrange  an  Erlenmeyer  suction  flask  with  a  dropping-funnel 
as  a  generator  for  hydrochloric  acid  gas.2  Place  about  25  grams 
of  sodium  chloride  in  the  flask  and  cover  it  with  cone,  hydro- 
chloric acid.  From  the  dropping-funnel  allow  cone,  sulfuric 
acid  to  drip  into  the  mixture.  Pass  a  slow  stream  of  the  gas 
through  an  empty  safety  bottle  and  then  into  a  250  cc.  wide- 
mouthed  bottle  through  a  tube  opening  above  a  solution  of  10  cc. 
of  the  purified  J-limonene  in  5  cc.  of  glacial  acetic  acid.  Keep  this 
solution  cold  by  placing  the  bottle  in  a  freezing  mixture  consisting 
of  ice  and  a  small  amount  of  salt.  The  unused  gas  is  not  allowed 
to  come  out  into  the  room,  but  is  absorbed  by  a  sodium  hydroxide 
solution  in  a  third  bottle,  as  the  bromine  vapors  were  absorbed 
in  the  experiment  for  preparing  ethylene  dibromide  (p.  43). 

1  If  only  a  very  crude  oil  is  available  purify  it  first  by  distilling  with  steam, 
drying  with  calcium  chloride,  and  subjecting  to  an  ordinary  distillation. 

2  A  very  convenient  generator  for  preparing  hydrogen  chloride  from  cone, 
hydrochloric  acid  and  cone,  sulfuric  acid,  is  described  by  Sweeney,  Journ.  Amer. 
Chem.  Soc.,  39  (1917),  2186. 

195 


196          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

In  a  short  time  the  liquid  solidifies  to  a  crystalline  mass.  About 
forty-five  minutes  is  required.  It  should  not  become  appre- 
ciably discolored.  Transfer  it  to  a  beaker  with  cold  water. 
Use  a  few  cc.  of  alcohol  to  dissolve  out  the  residual  particles  and 
add  this  to  the  main  portion.  Dilute  to  200  cc.,  stir  well,  and 
filter  off  the  solid  product  with  suction  in  a  Buchner  funnel 

(P.  52). 

Dissolve  the  product  in  about  45  cc.  -of  alcohol,  filter  from 
any  insoluble  particles,  and  pour  in  a  thin  stream,  with  stirring, 
into  200  cc.  of  cold  water.  The  dichlorterpane  separates  imme- 
diately in  small  white  crystalline  lumps.  Filter  again  with 
suction  and  press  out  with  a  spatula  1  on  the  smooth  side  of 
a  clean  porous  tile  (p.  56)  to  remove  the  last  traces  of  moisture. 
Since  the  substance  evaporates  very  slowly  when  left  in  the 
open,  it  must  be  covered  with  a  watch  glass  if  allowed  to  stand 
any  length  of  time  before  it  is  bottled.  7>a?w-i,8-dichlorterpane 
is  a  white  crystalline  solid,  melting  at  50°.  It  can  be  recrystal- 
lized  from  warm  alcohol.  Yield,  30  per  cent  of  the  theory. 

NOTES 

1.  Since  the  product  decomposes  "when  standing  in  the  presence 
of  acid,  the  experiment  should  be  completed  in  one  laboratory  period. 
If  this  is  not  possible,  let  the  product  remain  in  water. 

2.  The  cis-iorm  of  i,8-dichlorterpane  melts  at  25°  and  is  usually 
liquid  at  ordinary  temperatures.     If  this  is  obtained  instead  of  the 
solid  trans-iorm  it  is  probably  due  to  the  use  of  d-limonene  that 
has  not  been  properly  purified,  or  to  allowing  the  temperature  to  go 
too  high. 

3.  The  specific  gravity  of  d-limonene  is  0.846  at  18°. 

4.  The  substance  is  also  named  i,8-dichlor-menthane,  dipentene- 
dihydrochloride,  and  trans-terpm  dichloride. 

5.  If   the   dichlorterpane   does   not   crystallize  out  after  being 
poured  into  water  cool  the  entire  material  in  ice  and  then  remove  the 
lumps  and  press  them  out  on  a  porous  tile.  If  there  is  any  of  the  trans- 
form present  it  will  generally  remain  on  top  after  the  liquid  impurities 
have  been  absorbed.    Then  recrystallize  from  alcohol,  etc. 

1  If  a  steel  spatula  is  used  it  should  always  be  previously  cleaned  with  soap  to 
remove  traces  of  dust  and  rust. 


LABORATORY  EXPERIMENTS  197 


REFERENCES 

Cohen,  "  Organic  Chemistry  for  Advanced  Students,"  Pt.  Ill 
(1918),  Chap.  V;  Semmler,  "Die  Aetherischen  Oele,"  Vol.  II  (1906), 
339;  Stewart,  "  Recent  Advances  in  Organic  Chemistry,"  3d  Ed. 
(1918),  4i-52- 

• 
QUESTIONS 

1.  What  is  the  source  of  d-limonene? 

2.  Name  d-limonene  according  to  the  terpene  system  of  no- 

menclature. 

3.  What  does  the  "  d  "  in  d-limonene  and  the  "  trans  "  in  trans-i, 

8-dichlorterpane  signify? 

4.  Show  by  means  of  the  structural  formula  why  limonene  can 

exist  in  both  d-  and  /-  forms. 

5.  How  many  molecules  of  HC1  combine  with  each  molecule  of 

d-limonene,  and  how  can  this  be  shown  experimentally? 

6.  What  is  the  purpose  of  the  glacial  acetic  acid?    What  is  the 

melting-point  of  glacial  acetic  acid? 

7.  What  is  the  object  of  the  porous  tile?    Why  not  use  filter 

paper? 

8.  Why  must  the  product  not  be  left  in  the  open? 

9.  What  compound  is  formed  by  the  addition  of  HC1  to  propene? 

10.  Can  sodium  be  used  for  purifying  hydrocarbons  in  general? 

11.  Is   limonene    an    aromatic    or   hydroaromatic    compound? 

Why? 

12.  Of  what  use  in  terpene  chemistry  is  the  formation  of  the 

"  hydrochlorides  "? 


SYNTHESIS  OF  CAMPHOR  FROM  PINENE 

(!N  FIVE  STEPS) 
Experiment  No.  60 

(1)  Pinenehydrochloride  from  Pinene   (Rectified  Oil  of  Tur- 
pentine) 

Perform  this  experiment  under  the  hood,  or  connect  the 
outlet  tube  with  the  suction  pump  and  let  the  water  run  ver* 
slowly.  In  the  latter  case  pass  the  gases  through  a  tube  opening 
just  above  the  surface  of  a  2N  sodium  hydroxide  solution  con- 
tained in  a  bottle,  and  then  to  the  pump.1 

Provide  a  250  cc.  short-neck,  round-bottom  flask  with  a 
three-holed  rubber  stopper,  through  which  pass  (i)  a  gas  inlet 
tube  reaching  almost  to  the  bottom  of  the  flask,  (2)  a  calcium 
chloride  tube,  (3)  and  a  thermometer.  Saturate  200  grams  of 
pinene  contained  in  this  flask  with  dry  hydrogen  chloride, 
which  is  generated  in  the  following  apparatus.  Fit  up  an 
ordinary  liter  flask  or  bottle  with  a  dropping-funnel  and  an  outlet 
tube  inserted  through  a  two-holed  stopper.  Connect  this  (i) 
with  an  empty  wash  bottle,  (2)  with  a  Woulff  bottle  2  or  a  25o-cc. 
wide-mouthed  bottle  containing  cone,  sulfuric  acid,  provided 
with  a  safety  tube  2  feet  long,  (3)  another  wash  bottle  also  con- 
taining cone,  sulfuric  acid,  and  (4)  with  an  empty  wash  bottle, 
from  which  the  gas  is  led  into  the  pinene  flask.  The  empty  wash 
bottles  act  as  guards  and  prevent  any  danger  of  serious  explo- 
sions in  case  there  is  back  pressure  in  the  apparatus.  Use 
rubber  stoppers  and  glass  tubing  throughout,  joining  the  glass 

1  Test  the  apparatus  for  leaks  with  the  gas  under  pressure  before  turning  on 
the  water.     Otherwise  bubbles  of  air  may  be  mistaken  for  hydrogen  chloride. 

2  A  wide  bottle  with  three  apertures. 

198 


LABORATORY  EXPERIMENTS  199 

tubing  with  as  short  rubber  connections  as  possible.  The  two 
wash  bottles  with  sulfuric  acid  are  necessary  for  thoroughly 
drying  the  gas. 

The  pinene  flask  is  imbedded  in  a  mixture  of  cracked  ice 
and  a  small  amount  of  common  salt.  As  the  reaction  proceeds 
more  salt  may  be  necessary.  When  the  apparatus  is  all  ready 
put  500  grams  of  common  salt  in  the  generating  flask,  add 
enough  cone,  hydrochloric  acid  to  cover  the  salt,  and  then  allow 
cone,  sulfuric  acid  to  drop  upon  this  mixture  from  the  dropping- 
funnel.  The  gas  should  be  run  into  the  pinene  continuously 
at  a  fairly  rapid  rate  (about  two  hours  are  necessary),  care 
being  taken  that  the  temperature  does  not  exceed  20°.  The  re- 
action does  not  take  place  readily  below  o°.  The  best  tem- 
perature is  about  5°-i5°.  Sometimes  it  is  necessary  to  take 
the  ice  away  in  order  to  allow  the  temperature  to  rise  and  the 
reaction  to  start.  After  the  gas  has  been  passing  in  for  some 
time  the  temperature  may  rise  to  60°.  This  will  do  no  great 
harm,  other  than  to  color  the  mixture  on  account  of  slight 
decomposition,  but  the  temperature  should  not  be  allowed 
to  stay  up.  A  higher  temperature  should  be  avoided.  A 
slower  stream  of  gas  and  further  cooling  will  soon  bring  the 
temperature  down.  The  success  of  the  experiment  depends  upon 
the  dryness  of  the  gas  and  the  temperature  of  the  reaction. 

After  about  two  hours  when  no  more  gas  is  absorbed  and 
the  pinene  has  been  transformed  into  a  semi-solid  mass  disconnect 
the  flask  and  close  it  with  a  good  cork  or  rubber  stopper.  Cool 
it  to  —  10°  to  —  15°  in  a  freezing  mixture  consisting  of  about 
two  parts  of  cracked  ice  and  one  of  salt  and  let  it  remain  for 
thirty  minutes  or  overnight  (in  the  ice-box).  In  case  it  is  left 
overnight,  care  should  be  taken  that  no  water  from  the  melting 
ice  will  get  into  the  flask,  by  fastening  the  flask  upright  with  a 
clamp.  On  the  next  day  it  must  be  packed  again  and  cooled 
for  an  hour.  Filter  off  the  crystallized  pinenehydrochloride  with 
suction l  and  press  out  on  a  porous  tile.  Cool  the  filtrate  and 
thus  obtain  more  of  the  product.  Now  dissolve  the  entire 

1  It  is  convenient  to  use  a  flat-topped  glass  stopper  to  press  down  the  cake 
in  the  Buchner  funnel. 


200          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

crude  product  in  about  80  cc.  of  warm  alcohol  contained  in  a 
beaker  and  heated  on  the  steam-bath.  It  will  remain  milky 
white.  Then  cool  to  —  5°,  with  stirring  to  avoid  the  formation  of 
a  solid  mass.  Filter  and  press  out  as  above.  Yield,  100-125 
grams.  The  snow-white  crystalline  powder,  which  has  an  odor 
resembling  camphor,  melts  at  n8°-i2o°.  This  product  is 
used  for  the  next  experiment.  It  is  somewhat  volatile  at  the 
ordinary  temperature  and  pressure,  and  therefore  should  not  be 
left  uncovered  for  any  length  of  time. 

NOTES 

1.  Arrange  your  time  so  that  the  experiment  may  be  started  at 
the  beginning  of  a  laboratory  period.    The  pinenehydrochloride  should 
be  recrystallized  from  alcohol  the  same  afternoon  or  on  the  following 
day,  since  it  decomposes  slowly  on  standing.     If  it  does  not  crystallize 
after  the  gas  has  been  run  in  for  2\  hours,  the  pinene  used  probably 
contained  moisture  or  was  otherwise  impure,  or  the  temperature  was 
too  low. 

2.  Perfectly  pure  and  stable  pinenehydrochloride  which  melts 
at  125°  can  be  obtained  by  crystallization  from  petroleum  ether,  but  a 
large  amount  of  the  substance  is  lost  by  this  method. 

3.  At  one   time  pinenehydrochloride  was  known  as  "  artificial 
camphor,"    on    account    of    its    odor.     Now,    however,    this    is   a 
misnomer,  since  camphor  itself  can  be  synthesized. 

4.  Rectification  of  Oil  of  Turpentine.      Pinene  (boiling-point, 
155°)  is  the  chief  constituent  of  the  oil  of  turpentine.     It  is  obtained 
fairly  pure  by  distilling  the  oil  in  a  flask  with  metallic  sodium  and 
using  a  Young's  pear   fractionating   column  or  still-head  (Fig.  4, 
p.  25).      The  portion  going  over  between  154°  and  160°  consists 
almost  entirely  of  pinene.     For  this  experiment  use  300  cc.  of  crude 
pinene  and  about  4-5  grams  of  sodium. 

5.  The  brown  resinous  mass  remaining  in  the  flask  is  treated 
with  alcohol  to  destroy  any  unattacked  sodium  before  water  is  added 
and  then  the  flask  is  cleaned. 

6.  Save  a  specimen  of  at  least  i  gram  of  -each  of  the  products  in 
the  synthesis  of  camphor  from  pinene,  and  hand  them  in. 


LA?>3?v\:\);nr  EXPERIMENTS  201 


GENERAL  REFERENCES  FOR  STUDY 

Stewart,  "  Recent  Advances  in  Organic  Chemistry,"  3d  Ed. 
(1918),  Chap.  Ill;  and  Cohen,  "Organic  Chemistry  for  Advanced 
Students,"  2d  Ed.,  Pt.  Ill  (1918),  Chap.  V;  and  Semmler,  "  Die 
Aetherischen  Oele,"  Vol.  II  (1906). 

QUESTIONS 

1.  Outline  the  terpene  system  of  nomenclature  and  write  all  the 

reactions  in  the  synthesis  of  camphor  from  pinene  on  this 
basis,  using  only  the  skeleton  formula. 

2.  Discuss  Baeyer's  Strain  Theory. 

3.  Review  the  properties  of  the  olefmes  as  shown  by  their  reac- 

tions when  treated  with  (i)  halogens,  (2)  halogen  acids,  (3) 
hydrogen  in  presence  of  colloidal  platinum  or  finely  divided 
nickel  (at  high  temperature),  (4)  hypochlorous  acid, 
(5)  nitrosyl  chloride,  (6)  cone,  and  fuming  sulfuric  acid, 
(7)  ozone,  (8)  potassium  permanganate,  (9)  heat  alone,  or 
with  strong  acids  and  pressure. 

4.  What  addition  products  are  used  for  the  identification  of  the 

terpenes? 

5.  What  compounds  are  formed  when  pinene  is  treated  with 

moist  hydrochloric  acid,  and  particularly  with  alcoholic 
sulfuric  or  nitric  acids? 

6.  Is  pinene  regenerated  when  pinene  hydrochloride  is  boiled 

with  "  alcoholic  potash  "  or  potassium  phenolate?  What 
does  this  indicate? 

7.  Can  sodium  be  used  in  general  for  the  purification  of  hydro- 

carbons? 


Experiment  No.  61 
(2)  Camphene  from  Pinenehydrochloride 

In  a  400  cc.  round-bottomed  flask  melt  190  grams  of  phenol 1 
and  then  add  75  grams  of  potassium  hydroxide  2  (crushed).  The 
mixture  becomes  heated  spontaneously  and  the  alkali  dissolves. 
Shake.  Warm,  if  necessary,  to  produce  complete  solution. 
Now  connect  the  flask  with  a  condenser  for  distillation,  insert  a 
thermometer  with  the  bulb  in  the  neck  (not  in  the  liquid),  and 
carefully  heat  over  a  metal  gauze  to  distill  off  the  water  formed 
in  the  reaction.  A  small  amount  of  phenol  also  goes  over. 
After  the  temperature  reaches  150°  exchange  the  water  con- 
denser for  an  air  condenser.  When  all  the  water  has  been 
distilled  off  and  the  temperature  has  risen  to  180°,  allow  the 
flask  to  cool  somewhat,  disconnect,  and  add  100  grams  of  pinene- 
hydrochloride,3  in  three  portions,  the  second  and  third  after 
the  preceding  reaction  has  subsided.  Attach  an  upright  air 
condenser  to  the  flask  after  each  addition  and  heat  carefully 
at  first  since  there  may  be  a  violent  reaction.  Finally  keep  the 
mixture  boiling  for  two  or  three  hours,  shaking  the  flask  fre- 
quently. The  vapors  must  not  be  allowed  to  rise  more  than 
one-half  the  length  of  the  air  condenser.  //  the  heating  is  very 
strong,  fumes  will  come  out  of  the  top  and  these  will  settle  down  and 
become  ignited.  If  the  heating  is  interrupted  and  the  potassium 
phenolate  is  allowed  to  solidify  the  flask  must  be  cautiously 
heated  around  the  sides  until  the  solid  material  melts  before  heat 
is  applied  at  the  bottom. 

1  If  any  phenol  comes  in  contact  with  the  skin  apply  alcohol  at  once. 

2  Sodium  hydroxide  cannot  be  used  on  account  of  the  high  melting-point  of 
the  sodium  phenolate. 

3  Prepared  hi  the  previous  experiment. 

202 


LABORATORY  EXPERIMENTS  203 

Then,  in  order  to  obtain  the  camphene,  subject  the  mixture 
ro  distillation  in  the  same  manner  as  the  water  was  distilled 
above,  using  an  air  condenser,  until  the  temperature  of  the 
vapor  reaches  180°  (the  boiling-point  of  phenol).  At  first 
pure  camphene  distills  (i5o°-i6o°),  later  it  is  contaminated 
with  increasing  amounts  of  phenol.  The  distillation  is  stopped 
when  a  drop  of  the  distillate  entirely  dissolves  in  dilute  sodium 
hydroxide.  (Why?)  The  distillate  is  then  shaken  in  a  flask  with 
dilute  sodium  hydroxide  (Why?),  and  cooled  with  ice,  whereby 
the  camphene  solidifies  in  crystalline  lumps.  If  the  camphene 
does  not  crystallize  out  well  from  the  alkaline  solution,  warm, 
separate  and  then  cool.  Filter  with  suction  and  wash  with  ice 
water,  retaining  the  filtrate  for  recovering  the  phenol,  if  desired 
(see  below) .  If  a  small  amount  of  an  oily  constituent  should  pass 
through  the  filter  paper,  separate  it  from  the  remainder  of  the 
filtrate  and  add  to  the  main  portion.  Heat  the  camphene  in  a 
small  flask  on  the  steam-bath  until  it  melts.  When  it  is  liquid,  and 
a  good  separation  can  be  made,  pour  off  from  the  drops  of  water 
into  an  Erlenmeyer  flask  and  again  melt  in  the  same  way  with 
addition  of  a  few  pieces  of  calcium  chloride,  decant,  and  finally 
fractionate  in  a  round-bottomed  flask  surmounted  by  a  good 
fractionating  column  such  as  the  apparatus  of  Young  (Fig.  4, 
p.  25),  to  which  is  connected  an  air  condenser.  Protect  the 
distilling  apparatus  from  excessive  radiation  and  consequent  con- 
densation by  surrounding  it  with  paper  or  a  towel.  Collect  the 
fraction  distilling  between  155°  and  I600.1  This  solidifies  on 
cooling  to  a  colorless,  crystalline  mass.  Yield,  60  grams.  Pure 
camphene  melts  at  5i°-52°  and  boils  at  160°. 

The  product  should  be  chlorine-free.  Test  for  chlorine 
according  to  the  directions  on  p.  114.  If  the  product  is  not 
chlorine-free,  redistill  until  the  distillate  gives  no  test  for  halogen. 

The  residue  in  the  flask  contains  a  small  amount  of  pinene- 
hydrochloride. 

If  it  is  desired,  the  student,  may  recover  the  phenol  used 

1  Use  only  this  fraction  for  the  next  experiment.  The  lower  boiling  fraction 
(around  147°)  contains  other  hydrocarbons  which,  if  allowed  to  remain,  apparently 
causes  trouble  in  the  crystallization  of  the  isoborneol  later  on. 


204          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

in  this  experiment,  part  of  which  is  in  the  main  residue  and 
part  in  the  sodium  hydroxide  washings,  by  making  the  combined 
residues  acid  with  hydrochloric  acid  and  then  extracting  with 
ether.  Dry  the  ether  solution  for  twenty-four  hours  over  anhy- 
drous sodium  sulfate,  decant  and  remove  the  ether  in  the  ordinary 
way  by  distillation  and  then  distill  {he  phenol,  using  a  short  air 
condenser.  Boiling-point,  181.5°  Yield,  150-160  grams. 

QUESTIONS 

1.  Why   is   potassium   phenolate   used   instead   of   potassium 

alcoholate? 

2.  Why  not  use  sodium  phenolate? 

3.  How  is  the  camphene  separated  from  the  phenol? 

4.  Give  two  reactions  which  show  that  camphene  is  chemically 

different  from  bornylene. 

5.  What  is  formed  when  camphene  is  oxidized  with  chromic  acid? 


Experiment  No.  62 
(3)  Isobornylacetate  from  Camphene 

To  a  solution  of  50  grams  of  camphene  1  in  125  cc.  of  glacial 
acetic  acid  contained  in  a  flask,  add  a  mixture  of  2  cc.  of  cone, 
sulfuric  acid  and  3  cc.  of  water.  Warm  on  the  steam-bath 
to  5o°-6o°  (thermometer  in  the  flask)  for  i\  hours,  with 
frequent  shaking.  The  reaction  product  separates  in  two  layers 
at  first  which  finally  disappear  after  heating. 

Transfer  the  reddish-colored  solution  of  the  ester  to  a  large 
beaker,  rinse  the  flask  with  100  cc.  of  water  and  add  this  to  the 
beaker.  Neutralize  with  powdered  sodium  carbonate  crystals 
(about  300  grams).  Separate  and  dry  the  ester  with  calcium 
chloride,  and  then  fractionate  in  vacua.  At  12  mm.  pressure 
the  first  runnings  up  to  95°  contain  some  camphene;  the  main 
portion  then  distills  between  95°  and  105°  at  12  mm.,  chiefly 
ioo°-io2°.  Yield,  60  grams.  Isobornyl  acetate  is  a  colorless 
liquid  which  smells  like  valerian.  Specific  gravity,  0.9905  at 
15°.  Boiling-point,  102°  at  12  mm.;  io6°-io7°  at  15  mm. 

QUESTIONS 

1.  Explain  the  use  of  the  sulfuric  acid. 

2.  Why  is  the  crystalline  sodium  carbonate  preferred  to  the 

anhydrous    sodium    carbonate    or    to    sodium    hydrogen 
carbonate?     (Compare  heats  of  solution.) 

3.  Why  is  the  isobornyl  acetate  so  carefully  purified? 

1  Experiment  No.  61. 


205 


Experiment  No.  63 
(4)  Isoborneol  from  Isobornylacetate 

The  isobornylacetate  is  hydrolyzed  (saponified)  with  potas- 
sium hydroxide  and  converted  into  isoborneol  as  follows:  In  a 
250  cc.  flask  dissolve  50  grams  of  isobornylacetate l  in  a  solution 
of  100  cc.  of  alcohol  and  20  grams  of  potassium  hydroxide,  and 
heat  to  boiling  for  three  hours  under  reflux  condenser  on  the  steam- 
bath.  Pour  the  solution  into  cold  water.  The  isoborneol  separates 
as  a  white  or  light  yellow  solid.  If  it  remains  as  an  oil  or  a 
semi-solid  mass,  place  the  beaker  in  ice  and  stir  with  a  mechanical 
stirrer  2  for  |  to  2  hours.  The  isoborneol  gradually  becomes  white 
and  crystalline.  If  it  does  not  crystallize,  but  remains  as  an  oil 
or  an  oily  lump,  separate,  add  fresh  water,  and  stir  again.  Break 
up  any  lumps.  Or  continue  the  hydrolysis  with  fresh  "  alco- 
holic potash  "  for  J  to  i  hour.  Filter  off  the  crystals  with 
suction,  and  wash  with  cold  water,  press  out  and  dry  on  a  porous 
tile.  Melting-point  of  this  crude  product,  203°-205°.  Yield, 
35  grams.  The  isoborneol  thus  obtained  is  pure  enough  for  con- 
version into  camphor,  as  described  in  the  next  experiment. 
Crystallized  from  petroleum  ether,  absolutely  pure  isoborneol 
is  obtained,  melting  at  212°  (in  a  closed  tube,  see  foot-note  7, 
p.  66). 

QUESTIONS 

1.  Compare  the  preparation  of  glycol  from  ethylene  dibromide 

through  the  acetate. 

2.  How  can  ethyl  alcohol  be  prepared  from  ethylene? 

1  Experiment  No.  62. 

2  An  electric  mixer  such  as  are  used  at  soda  water  fountains  is  excellent  for  this 
purpose. 

206 


LABORATORY  EXPERIMENTS 


207 


3.  What  chemical  reaction  of  isoborneol  shows  that  it  is  a 

tertiary  alcohol? 

4.  Why  cannot  a  good  melting-point  of  isoborneol  be  taken  in 

an  open  tube? 

5.  How  does  changing  the  water  aid  in  the  crystallization  of  the 

product? 

6.  Is  alcoholic  KOH  generally  used  for  hydrolysis?     (Compare 

the  analysis  of  fatty  oils,  etc.) 

7.  How  can  tertiary  alcohols  be  prepared  by  the   Grignard 

reaction? 


Experiment  No.  64 
(5)  Camphor  from  Isoborneol 

Perform  this  experiment  under  the  hood  or  near  the  draft  pipe. 
Make  a  mixture  of  60  grams  of  concentrated  nitric  acid  (sp.gr. 
1.42)  and  12  grams  of  red  fuming  nitric  acid  (sp.gr.  1.60)  in  a 
250  cc.  flask,  cool  to  2o°-25°,  and  keeping  the  temperature  be- 
tween 2o°-25°,  cautiously  add  in  small  amounts  30  grams  of 
isoborneol.1  Each  portion  of  isoborneol  dissolves  in  the  acid 
with  rise  in  temperature  and  evolution  of  nitric  oxides.  During 
the  operation  the  mixture  must  be  well  stirred,  shaken  and 
cooled.  At  the  end,  a  compound  of  camphor  and  N20s  separates 
as  a  slightly  colored  oily  layer.  Continue  the  stirring  and 
shaking  as  much  as  possible  for  about  thirty  to  forty  minutes, 
and  then,  while  shaking,  slowly  pour  out  the  contents  into  some 
cracked  ice  in  a  beaker.  The  camphor  separates  out  in  white 
lumps.  If  it  does  not,  melt  the  ice,  separate,  and  add  cold 
water  to  the  camphor  layer.  It  will  then  crystallize  out,  espe- 
cially on  cooling.  Filter  with  suction  and  wash  with  ice  water. 
This  crude  product  melts  at  about  168°  and  contains  some 
oxides  of  nitrogen.  In  order  to  purify  the  camphor  treat  it  in 
a  500  cc.  flask  with  a  dilute  solution  of  3  grams  of  sodium  hydrox- 
ide and  5  grams  of  potassium  permanganate,  and  then  distill 
with  steam  through  an  air  condenser2  into  a  wide-mouthed  bottle 
which  is  cooled  in  cold  running  water.  Dry  the  purified  pro- 
duct on  a  porous  tile.  It  should  be  perfectly  white,  and  melt  at 
i72°-i73°.  Yield,  21  grams.  Camphor  is  volatile  and  care 
must  be  used  to  carry  on  all  operations  under  good  cooling. 

1  Experiment  63. 

2  The  camphor  separates  out  in  a  water  condenser,  and  therefore  if  one  is  used 
the  distillation  must  be  discontinued  now  and  then,  and  the  camphor  pushed  out 
with  a  long  rod.     Otherwise  it  will  clog  the  condenser. 

208 


LABORATORY  EXPERIMENTS  209 

By  neutralizing  the  nitric  acid  nitrate  obtained  above  with 
sodium  carbonate  and  distilling  this  with  steam,  about  2.5  grams 
more  of  camphor  can  be  obtained. 

NOTES 

1.  Do  not  leave  the  product  in  the  open  air  longer  than  is  neces- 
sary to  press  out  on  the  porous  plate. 

2.  ^/-Camphor  melts  at  175°,  boils  at  209°,  and  sublimes  at  the 
ordinary  temperature;  sp.gr.  0.992  at  10°.     Camphor  obtained  from 
isoborneol  consists  of  a  racemic  mixture.     Camphor  from  the  camphor 
tree  (Laurus  camphora)  is  dextro-rotary. 


REFERENCE  AND  ACKNOWLEDGMENT 

This  series  of  experiments  in  the  synthesis  of  camphor  is  based 
upon  those  given  in  Ullmann's  "  Organisch-Chemisches  Praktikum" 
(1908),  230-6,  and  the  author  is  glad  to  make  acknowledgement  here. 


QUESTIONS 

1.  How  is  camphor  obtained  from  isoborneol? 

2.  Point  out  the  asymmetric  carbon  atoms  in  camphor. 

3.  Is  the  product  obtained  optically  active?     Why? 

4.  Give  several  reactions  which  show  that  camphor  is  a  ketone. 

5.  How  can  it  be  shown  that  there  is  a  CH2-group  adjacent  to  the 

carbonyl  group? 

6.  Discuss  the  oxidation  products  of  camphor. 

7.  Outline  Komppa's  synthesis  of  camphoric  acid. 

8.  How  can  camphor  be  synthesized  from  camphoric  acid? 


Experiment  No.  65 

DIRECT  OXIDATION  or  A  HYDROCARBON 
Anthraquinone  from  Anthracene 

Connect  a  flask  containing  2.5  grams  of  anthracene  with  an 
addition  tube  and  a  reflux  condenser.  Pour  in  20  cc.  of  glacial 
acetic  acid  and  heat  on  the  steam-bath.  Prepare  a  solution  of 
4.5  grams  of  chromium  trioxide  in  a  little  water  and  add  7  cc. 
of  glacial  acetic  acid.  Add  this  solution  in  small  amounts  to 
the  flask  and  continue  the  heating  for  five  minutes  after  the 
addition  of  the  last  portion.  It  will  not  all  dissolve.  Pour 
the  green  mixture  into  water,  and  stir  well.  Filter  off  the 
precipitate  with  suction,  wash,  and  dry  it.  Recrystallize  as 
follows:  Pour  over  the  dry  product  in  a  flask  no  cc.  of  toluene. 
Connect  with  an  upright  condenser  and  heat  carefully  over  a 
wire  gauze  to  boiling  for  several  minutes.  Do  not  use  such  a 
large  flame  that  some  of  the  vapors  come  uncondensed  out  of  the 
top  of  the  condenser.  The  vapors  are  heavy  and  will  settle 
down  and  become  ignited.  The  solubility  of  anthraquinone 
is  2.56  parts  in  100  parts  of  toluene  at  100°.  Immediately  after 
disconnecting,  filter  the  solution  through  a  fluted  l  filter  paper 
in  a  glass  funnel  set  in  a  hot-water  funnel,2  using  a  stirring- 
rod  to  direct  the  flow  of  the  hot  solution  into  the  filter.  When 
filtering  inflammable  liquids,  the  burner  under  the  side  tube 
must  always  be  removed.  The  anthraquinone  rapidly  crystal- 
lizes out.  It  is  separated  with  suction3  and  allowed  to  dry 

^eep.  128. 

2  See  p.  128. 

3  If  it  is  desired  to  concentrate  the  toluene  solution,  distill  off  the  toluene  in  the 
usual  way  from  a  distilling  flask.    This,  however,  generally  gives  dark-colored 
crystals. 

210 


P  LABORATORY  EXPERIMENTS  211 

• 
between  filter  papers.    Large  well-formed  crystals  are  obtained 

if  the  filtrate  is  allowed  to  cool  very  slowly.  This  can  be  done 
by  placing  the  beaker  in  warm  water  and  letting  all  cool  together. 
However,  the  finer  crystals  formed  by  rapid  cooling  are  more 
likely  to  be  the  purer  product.  Melting-point  285.5°,  cor. 
Yield,  2.5  grams. 

Sublime  a  sample  of  the  anthraquinone  as  follows:  Place 
i  a  small  amount  of  the  material  on  an  8-cm.  watch  glass,  cover 
with  an  8-cm.  filter  paper  which  has  been  perforated  with  a 
number  of  tiny  holes,  and  then  put  another  watch  glass  of  the 
same  size,  convex  side  up,  over  these.  Set  on  a  wire  gauze 
and  place  a  very  small  flame  underneath.  Light-yellow  crystals 
soon  begin  to  deposit  on  the  cold  surface  of  the  upper  watch 
glass  and  the  paper  will  prevent  them  from  falling  back  to  the 
lower  one.  An  inverted  funnel  can  be  used  instead  of  the  upper 
watch  glass.  Determine  the  melting-point  of  this  sublimed 
sample  as  well  as  of  the  recrystallized  product. 


QUESTIONS 

1.  Is  anthraquinone  a  true  chemical  derivative  of  anthracene? 

2.  Compare   anthracene   and   diphenylme thane   in  regard   to 

oxidation  with  chromic  acid. 

3.  Does    anthraquinone    have    any    aliphatic  characteristics? 

Compare  it  with  ^-benzoquinone. 

4.  Explain  why  you  should  expect  the  9  and  10  carbon  atoms 

of  anthracene  to  be  more  easily  oxidized  than  the  others. 

5.  What  naturally  occurring  dye  is  related  to  anthraquinone? 

6.  To  what  is  the  green  color  of  the  reaction  mixture  due? 

(Compare  question  4,  Acetaldehyde  Ammonia,  Expt.  17, 

p.  88.) 
Why  cannot  alcohol  or  water  be  used  in  place  of  the  acetic 

acid  in  this  experiment? 
Why  is  a  fluted  filter  paper  used? 
Why  are  the  finer  crystals  more  likely  to  be  purer? 

10.  Explain  sublimation. 

11.  Does  anthraquinone  contain  auxochrome  or  chromophore 

groups? 

12.  How  can  anthraquinone  be  reconverted  into  anthracene? 


212          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

13.  What  compound  is  formed  when  anthraquonine   is  shaken 

with  zinc  .dust  and  sodium  hydroxide   solution?     How 
can  this  be  changed  back  into  anthraquinone? 

14.  Discuss  quinone  monoxime  relative   to  its   structure   and 

method  of  preparation  from  quinone,  and  from  phenol. 

15.  What  are  the  naphtho-quinones?     How  prepared? 


Experiment  No.  66 

• 

NITROGEN  HETEROCYCLES 
Pyridine 

1.  Dissolve  a  few  drops  of  pyridine  in  pure  ammonia-free 
water  and  test  its  reaction  with  neutral  litmus. 

2.  To  an  aqueous  solution  of  pyridine  add  a  drop  or  two  of 
i  molar  ferric  chloride  solution.     (?) 

3.  Mix  i  cc.  of  pyridine  and  0.9  cc.  of  methyl  iodide  l  in  an 
ordinary  No.  2  test-tube  supported  in  a  rack.     Stir  with  a  ther- 
mometer.    A  vigorous  reaction  sets  in  and  a  yellowish  solid  is 
formed.     Note    the    temperature    as    the    reaction    continues. 
It  may  become  so  hot  that  the  product  melts.     Recrystallize 
the  product  by  adding  5  cc.  of  absolute  alcohol  and  heating  the 
tube  in  warm  water  until  solution  takes  place,  and  then  allow 
to  cool.     Filter  with  suction  and  wash  the  crystals  with  a  small 
amount  of  cold  absolute  alcohol.     The  crystals  are  usually  in  the 
form  of  fUt  pencils  which  are  sometimes  aggregated  in  rosettes. 
They  very  slowly  deliquesce.     Melting-point,  117°. 

Test  the  solubility  of  a  small  portion  of  the  recrystallized 
product  in  water.  To  this  solution  add  a  drop  of  silver  nitrate 
solution.  Is  there  an  immediate  precipitate?  What  is  it? 
Account  for  it. 

Quinoline 

1.  Test   the   solubility   of   quinoline   in   water.     Does   the 
aqueous  layer  react  alkaline  toward  litmus? 

2.  Add  a  little  hydrochloric  acid  to  a  few  drops  of  quinoline 
in  water.     (?) 

1  Methyl  iodide  is  somewhat  poisonous.      Be  careful  not  to  breathe  its  vapors  or 
get  it  on  the  skin. 

213 


214          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

3.  To  a  hydrochloric  acid  solution  of  quinoline  add  a  solu- 
tion of  potassium  dichromate.     (?) 

QUESTIONS 

.  PYRIDINE 

1.  Write  the  equation  to  show  the  substances  formed  in  the 

condition  of  equilibrium  when  pyridine  is  dissolved  in 
water. 

2.  Explain  the  action  of  the  aqueous  solution  of  pyridine  on 

ferric  chloride.     What  is  the  precipitate? 

3.  What  type  of  substance  is  formed  by  the  reaction  between 

pyridine  and  methyl  iodide?     Write  its  structure. 

4.  Explain  the  action  of  silver  nitrate  on  the  aqueous  solu- 

tion of  the  pyridine  iodmethylate  (or  methiodide).  Com- 
pare with  ethylammonium  chloride  used  in  a  previous 
experiment  (under  Methyl  Amine,  p.  121). 

5.  What  is  formed  when  the  pyridine  iodmethylate  is  treated 

with  potassium  hydroxide? 

6.  What  is  formed  when  the  pyridine  iodmethylate  is  heated 

alone  to  300°?  Compare  with  the  preparation  of  o-  and 
/>-toluidine  from  methyl  aniline. 

7.  How  could  you  tell  experimentally  when  a  substance  con- 

tains a  tertiary  nitrogen  atom  as  in  pyridine  and  when  it 
contains  a  secondary  nitrogen  atom  as  in  pyrrole,  coniine, 
etc.? 

8.  Look  up  the  formulas  for  nicotine,  coniine,  tryptophane  and 

indigo.     What  nitrogen  heterocycles  do  they  contain? 

QUINOLINE 

9.  Write  the  structures  of  the  compounds  formed  when  quino- 

line is  treated  with  hydrochloric  acid,  and  this  solution 
with  potassium  dichromate. 

10.  Why  does  the  quinoline  dissolve  in  dilute  hydrochloric  acid? 

11.  How  can  quinoline  be  prepared  synthetically? 

12.  How  does  isoquinoline  differ  from  quinoline? 

13.  Look  up  some  alkaloids  which  contain  the  quinoline  nucleus; 

also  the  isoquinoline  nucleus, 


PART  n 
ORGANIC  COMBUSTIONS 


FOREWORD 


THE  determination  of  carbon  and  hydrogen  and  of  nitrogen 
in  organic  substances  is  very  important  because  it  is  fundamental, 
and  yet,  in  spite  of  its  importance,  the  operations  are  not  always 
as  successful  as  they  should  be,  and  are  often  regarded  in  organic 
laboratories  as  a  somewhat  "  necessary  nuisance,"  and  as  F.  G. 
Benedict  says,1  "  exasperatingly  vexatious."  It  is  practically 
impossible  to  find  a  commercial  laboratory  that  will  undertake 
the  task,  and  usually  one  must  set  up  his  own  apparatus  and 
attend  to  it  himself  unless  he  is  so  fortunate  as  to  be  located 
in  a  large  research  laboratory  where  someone  is  employed  for 
this  sole  purpose. 

Organic  combustions,  as  the  operations  are  commonly  called, 
will  continue  to  be  more  or  less  difficult,  since  some  variation  must 
be  added  in  the  case  of  each  individual  substance.  Combustions 
should  be  considered  as  a  means  to  an  end,  not  the  end  in  itself, 
and  therefore  the  methods  should  be  so  clearly  and  exactly  defined 
that  they  can  be  carried  out  with  the  greatest  possible  accuracy 
in  the  minimum  amount  of  time  and  with  the  smallest  amount 
of  energy.  If  all  the  mechanical  details  and  the  more  useful 
forms  of  apparatus  are  adequately  described  and  the  pitfalls  in 
manipulation  pointed  out,  there  is  no  good  reason  why  anyone 
with  a  knowledge  of  and  skill  required  in  ordinary  quantitative 
analysis  should  not  be  able  to  master  the  method  and  obtain 
good  results  from  the  very  beginning.  Accordingly,  if  the  direc- 
tions in  the  following  pages  come  anywhere  near  accomplishing 
this  end,  the  hopes  of  the  author  will  be  realized. 

The  methods  selected  for  description  are  the  outgrowth  of  our 
experience  covering  several  years.     Like  most  workers  in  the 
subject  the  author  has  taken  the  liberty  of  describing  some  of  his 
own  modifications,  especially  in  apparatus,  and  he  is  willing  to 
assume  the  responsibility  for  the  direct  statements  made  herein. 
1 "  Elementary  Organic  Analysis/'  Preface. 
216a 


216b  FOREWORD 

Where  he  has  not  been  very  familiar  with  a  certain  procedure  or 
with  certain  kinds  of  apparatus  he  has  tried  to  show  that  lack 
in  the  wording  of  the  text.  The  descriptions  ordinarily  refer  to 
work  on  the  common  organic  compounds  usually  met  with  in 
laboratory  practice. 

It  is  believed  that  many  of  the  difficulties  in  carrying  out  an 
organic  combustion  arise  from  the  fact  that  the  operator,  as  is 
very  natural,  is  not  thoroughly  familiar  with  the  apparatus  and 
its  possibilities.  For  this  reason,  the  •  apparatus  has  been  very 
carefully  described,  and  many  of  those  little  "  kinks  "  which  are 
very  helpful  but  not  always  available  in  writing  are  also  added. 
Lest  the  student  lose  track  of  his  work  on  account  of  the  length 
of  some  of  the  descriptions  and  notes,  he  is  referred  to  the 
important  "  Topical  Outline  of  General  Method  of  Procedure," 
which  is  a  concise  summary  of  the  necessary  operations  arranged 
to  save  both  time  and  energy.  It  must  be  remembered  that  you 
cannot  run  a  combustion  just  by  keeping  a  set  of  directions 
beside  your  apparatus.  You  must  study  the  method  in  detail. 
Then  the  topical  outline  will  help  bridge  the  gaps. 

The  author  has  tried  to  give  due  credit  to  the  proper  authori- 
ties in  special  cases  by  numerous  references  in  appropriate  places. 
Acknowledgments  are  hereby  gladly  made  to  such  standard 
works  as: 

Gattermann's  "  Practical  Methods  of  Organic  Chemistry  "; 
W.  A.  Noyes'  "  Organic  Chemistry  for  the  Laboratory  "; 
Sudborough  and  James'  "  Practical  Organic  Chemistry  "; 
Cohen's  "  Practical  Organic  Chemistry  "; 
F.  G.  Benedict's  "  Elementary  Organic  Analysis  "; 
Dennstedt's  "  Anleitung  zur  vereinfachten  Elementaranalyse." 

The  author  also  wishes  to  extend  his  grateful  thanks  for  many 
helpful  suggestions  to  his  colleagues,  especially  Professors  John 
M.  Nelson,  H.  T.  Beans,  and  Harold  A.  Fales,  and  to  his  former 
students  and  co-workers  in  the  organic  laboratory  at  Columbia 
University,  who  have  borne  with  him  in  his  efforts  to  standardize 
organic  combustions  and  to  make  them  more  easy  and  fruitful. 

HARRY  L.  FISHER 

COLUMBIA  UNIVERSITY,  NEW  YORK, 
June,  1919. 


DIVISION  A 

THE  DETERMINATION  or  CARBON  AND  HYDROGEN 

I.  Historical 1  Introduction 

In  the  year  1781  Lavoisier,  working  on  the  theory  of  combus- 
tion, established  with  a  fair  degree  of  accuracy  the  quantitative 
relation  of  carbon  and  oxygen  to  carbon  dioxide,  and  of  hydrogen 
and  oxygen  to  water,  and  also  showed  that  carbon  dioxide  and 
water  were  the  sole  products  of  the  combustion  of  organic  sub- 
stances such  as  "  spirit  of  wine,"  oil,  wax,  sugar,  and  resins. 
In  1784  he  burned  weighed  portions  of  some  of  these  organic 
substances  in  a  known  volume  of  oxygen,  and  collected  the 
gaseous  products  in  a  bell- jar  over  mercury.  These  gaseous 
products  he  analyzed  by  volume,  absorbing  the  carbon  dioxide 
in  a  potash  solution,  and  measuring  the  residual  oxygen.  He 
then  calculated  the  weight  of  the  water  indirectly,  and  in  this  way 
he  was  able  to  determine  the  composition  of  the  substance.2  For 
the  more  difficultly  combustible  substances  he  used,  instead  of  free 
oxygen  gas,  mercuric  oxide  and  manganese  dioxide,  which  give 
up  oxygen  when  heated.3  Thus  he  laid  the  very  foundations  of 
elementary  organic  analysis. 

1  Dennstedt  has  given  us  an  excellent  detailed  account  of 'the  historical  develop- 
ment of  organic  combustions  in  his  article,  "  Die  Entwickelung  der  organischen 
Elementaranalyse,"  in  Ahrens'  "  Sammlung  chemischer  und  chemisch-technischer 
Vortrage,"  IV  (1899),  1-114.  The  article  also  contains  a  very  complete  bibliog- 
raphy. 

2Ladenburg,  "  History  of  Chemistry,"  trans,  by  Dobbin  (1899),  289. 

3  Ernst  von  Meyer,  "  A  History  of  Chemistry,"  trans,  by  George  McGowan, 
3d  English  edition  (1906),  410-2;  Armitage,  "A  History  of  Chemistry,"  (1906), 
54.  Dennstedt,  on  pages  2  and  3,  of  his  history  mentioned  above,  gives  a  detailed 

217 


218          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

Gay-Lussac  and  Thenard,1  in  1810,  extended  Lavoisier's 
work  and  modified  the  method  of  burning  the  substance  by 
mixing  it  with  a  known  weight  of  potassium  chlorate.  The 
mixture  was  worked  into  a  paste  with  water  and  formed  into 
pellets,  which  were  dried  in  an  air-bath  and  dropped  into  a 
hot  vertical  tube.  The  gases  given  off  were  collected  over 
mercury  and  analyzed  as  in  gas  analysis.  The  results  obtained 
were  considered  as  accurate  as  the  best  mineral  analyses  known 
at  that  time.  Violent  explosions  often  occurred  in  this  method, 
and  Berzelius2  in  1817  made  a  marked  improvement,  which 
reduced  the  possibility  of  an  explosion  to  a  minimum.  He 
mixed  the  organic  substance  with  potassium  chlorate  and  a 
large  amount  of  sodium  chloride,  and  then  gradually  decom- 
posed this  mixture  by  heating  in  a  horizontal  tube.  He  was 
the  first  to  pass  the  gases  through  a  straight  tube  contain- 
ing fused  calcium  chloride,  and  thus  he  obtained  directly  the 
amount  of  water  absorbed  by  weighing  the  tube  before  and 
after  the  combustion.  He  also  determined  the  carbon  dioxide 
directly  by  weight.  For  this  purpose  he  used  solid  potassium 
hydroxide  which  was  contained  in  a  small  glass  vessel.  It 
was  weighed  before,  and  after  standing  in  the  bell-jar  for  twenty- 
four  hours,  it  was  weighed  again.  It  was  no  longer  necessary 
to  take  into  account  the  residual  oxygen. 

Cupric  oxide  was  introduced  as  the  oxidizing  agent  by 
Gay-Lussac3  in  1815,  and  its  general  use  thenceforth  was 
established. 

account  of  the  method  with  illustrations  of  the  apparatus,  used  by  Lavoisier. 
Compare  H.  Meyer,  "  Analyse  und  Konstitutionsermittelung  organischer  Ver- 
bindungen,"  2.  Auflage  (1909),  146-53. 

A  short  history  of  organic  combustions  is  also  given  in  Lassar-Cohn's  "  Arbeits- 
methoden,"  Allgemeiner  Teil,  Vierte  Auflage  (1906),  274-5. 

For  early  work  and  analyses,  see  the  following  books  by  Emil  T.  Wolff,  which 
•are  replete  with  examples  and  references,  although  no  description  of  the  methods 
is  given;  "Quellen  Literatur  der  theoretisch-organisher  Chemie"  (1845),  18-26; 
and  "  Vollstandige  Uebersicht  der  Elementar-analytischen  Untersuchungen  organ- 
ischer Substanzen"  (1846).  The  author  is  indebted  to  Prof.  F.  B.  Dains  for 
Wolff's  work. 

1Dennstedt,  9;  Armitage,  129. 

2  Dennstedt,  10-11;  von  Meyer,  412. 

3Dennstedt,  12;  von  Meyer,  413;  Armitage,  139. 


ORGANIC  COMBUSTIONS  219 

The  U-form  of  tube  for  calcium  chloride  appeared  in  1822, 
being  first  used  by  Bussy.1 

The  whole  procedure  of  organic  combustions  was  put  upon  a 
firm  basis  by  the  very  careful  and  painstaking  work  of  Justus 
von  Liebig,  who  improved  the  details  and  simplified  the  deter- 
mination of  carbon  dioxide  by  the  introduction  of  a  convenient 
bulb-shaped  apparatus — the  Liebig  potash  bulb.2 

For  many  years  Liebig's  outline  was  the  standard.  Modi- 
fications were  introduced,  especially  in  the  manner  of  heating 
the  tube.  He  had  used  a  charcoal  furnace.  This  was  replaced 
first  by  gas  furnaces  and  now  by  electric  combustion  furnaces. 
Oxygen  3  was  used  instead  of  air  in  some  instances.  Soda  lime 
was  first  used  in  1858  by  Mulder.4  It  absorbs  carbon  dioxide 
more  rapidly  than  the  potassium  hydroxide  solution  and  is  more 
convenient  to  handle.  The  chief  modification  was  brought  out 
by  Kopfer  5  in  1876,  who  used  platinum  black,  and  later  platin- 
ized asbestos,  as  a  catalytic  oxidizing  agent,  burning  the  sub- 
stance in  a  stream  of  oxygen,  without  any  copper  oxide,  etc.  In 
this  method  the  tube  is  shortened  and  only  a  few  gas  burners 
are  required;  furthermore,  the  combustion  itself  can  be  car- 
ried out  in  a  much  shorter  time,  and  many  organic  substances 
which  could  not  be  properly  burned  by  the  older  method  could 
be  burned  completely.  Kopfer's  method  was  improved  by 
F.  Blau,6  but  has  been  perfected  and  most  successful  in  the 


lJourn.  de  Pharm.  (1822),  580;  Dennstedt,  TO. 

2Dennstedt,  18-20;  von  Meyer,  413;  Armitage,  149.  Liebig,  "  Ueber  einen 
neuen  Apparat  zur  Analyse  organischer  Korper  und  iiber  die  Zusammensetzung 
einiger  organischen  Substanzen,"  Poggendorff's  Annalen,  21  (1831),  i. 

Liebig  published  the  details  of  the  method  in  a  pamphlet  entitled,/'  Anleitung 
zur  Analyse  organischer  Korper,"  (1837);  a  second  edition  being  published  in 
1853.  It  was  translated  into  English  by  Wm.  Gregory,  and  published  in  1839 
under  the  title,  "  Instructions  for  the  Chemical  Analysis  of  Organic  Bodies." 

3  Dumas  and  Stass  first  used  oxygen  in  combustions  in  redetermining  the  atomic 
weight  of  carbon.  See  Dennstedt,  77.  Liebig  had  used  air  in  his  combustion 
method. 

*Jahresber.  (1858),  589;  Dennstedt,  28. 

5Ber.,  9  (1876),  1377;  Zeitschr.  anal.  Chem.,  17  (1878),  i;  Dennstedt's 
history,  81. 

6Monatshefte  fur    Chemie,  10  (1889),  357-71. 


220          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

hands  01  Dennstedt.1  It  requires  a  double  inlet  for  two  carefully 
regulated  streams  of  oxygen.  One  stream  goes  through  a  short 
inner  tube  which  contains  the  boat  and  substance,  and  the  other 
stream  goes  outside  this  tube,  and  furnishes  an  abundant  supply 
of  oxygen  just  as  the  products  of  combustion  come  out  of  the 
inner  tube  and  meet  the  catalyst.  Considerable  practice  is 
necessary  to  handle  the  operation,  but  it  gives  excellent  results. 
The  platinum  is  "  poisoned  "  by  some  substances  and  requires 
frequent  treatment  with  cone,  hydrochloric  acid  to  activate  it. 

Another  method,  which  was  being  developed  at  about  this 
time  but  which  has  not  yet  seen  its  full  development,  is  the 
combustion  of  the  substance  in  a  bomb  with  oxygen  under 
pressure.2  There  have  been  many  limitations  in  experimenting 
with  this  method,  but  these  are  gradually  disappearing  with  the 
perfecting  of  the  bombs  for  calorimetric  work,  and  the  present 
author  feels  that  the  day  will  soon  come  when  the  variations  in  the 
burning  of  each  individual  substance  will  no  longer  cause  any 
difficulty,  since  it  will  be  possible  to  have  a  bomb  in  which  any 
substance  can  be  burned  within  a  few  seconds  under  the  same 
general  conditions,  and  connections  arranged  for  the  absorption 
of  both  water  vapor  and  carbon  dioxide  in  the  usual  manner. 

The  use  of  platinum  as  a  catalyst  heated  by  a  burner  outside 
a  combustion  tube  naturally  led  to  the  electrical  heating  of  the 
platinum.  This  method  has  been  shown  to  be  rapid  and  very 
efficient,  but  the  apparatus  is  not  generally  available.  It  was 
first  described  by  Morse  and  Taylor3  in  1905,  and  is  given  in 

1  Dennstedt,  "  Anleitung  zur  vereinfachten  Elementaranalyse,"  (1903);  Dritte 
Auflage  (1910). 

Also,  H.  Meyer,  "  Analyse  und  Konstitutionsermittelung  organischer  Ver- 
bindungen,"  2.  Auflage  (1909),  170-6;  Gattermann,  "  Practical  Methods  of 
Organic  Chemistry,"  3d  English  ed.  (1914),  113-29;  and  Sudborough  and  James, 
"  Practical  Organic  Chemistry,"  (1915),  50-5. 

2Berthelot,  Comp.  rend.,  114  (1892),  318;  129  (1899),  Io°2;  Ztschr.  anal. 
Chem.,  40  (1901),  124;  Hempel,  Ber.,  30  (1897),  202;  Zuntz  and  Frentzel,  Ber., 
30  (1897),  381;  Langbein,  Ztschr.  angew,  Chem.,  Year  1900,  1227,  1259;  and 
Year  1901,516. 

The  method  is  also  described  in  the  catalogue  of  the  Emerson  Fuel  Calorimeters 
(1915),  17-23. 

3  Morse  and  Taylor,  Amer.  Chem.  Journ.,  33  (June  i,  1905),  591;  and  Morse 
and  Gray,  Amer.  Chem.  Journ.,  35  (1906),  451;  and  almost  at  the  same  time  by 


ORGANIC  COMBUSTIONS  221 

detail  in  Morse's  "  Exercises  in  Quantitative  Analysis,"  (1905), 

537-45- 

All  these  combustion  methods  require  from  0.2-0.5  gram  of 

substance  for  each  determination.  Oftentimes  such  an  amount  is 
not  available,  and  on  this  account,  Pregl :  devised  a  scheme  by 
which  it  is  possible  to  make  a  complete  analysis  for  carbon 
and  hydrogen  on  only  0.005  gram  of  the  substance.  Platinum 
as  the  catalyst  or  cupric  oxide  on  asbestos  are  used  in  a  tube 
about  20-40  cm.  long.  A  special  balance 2  is  required.  The 
method  is  spoken  of  as  micro-combustion  in  contradistinction 
to  the  ordinary  method,  which  is  termed  macro-combustion. 

In  1913  Bekk3  published  a  modification  of  Dennstedt's 
method  using  cerium  dioxide  as  the  catalyst  instead  of  platinum, 
and  by  using  a  long  train  of  the  catalyst  (30  cm.  of  the  tube 
filled  with  cerium  dioxide  deposited  on  asbestos)  and  by  placing 
the  substance  in  a  special  small  tube  inside  the  larger  com- 
bustion tube  he  was  able  to  do  away  with  Dennstedt's  com- 
plicated double  inlet.  He  claimed  even  greater  rapidity  for  his 
method  over  Dennstedt's,  and  furthermore  showed  that  the 
cerium  dioxide  was  not  only  an  excellent  catalyst,  but  also  that 
it  was  much  cheaper  and  not  "  poisoned  "  by  the  common 
materials  that  destroy  the  catalytic  action  of  the  platinum. 

Carrasco,  Atti  R.  Accad.  del  Lincei  Roma  [5]  14,  II,  608-18  (Dec.  3,  1905);  Chem. 
Central,,  1906  (I),  699-701.  See  also  Bretau  andLeroux,  Comp.  rend.,  145  (1907), 
524-6,  Chem.  Central.,  1907  (II),  1653. 

1  Pregl,  "  Die  quantitative  Mikroelementaranalyse  organischer  Substanzen," 
in  Abderhalden's  "  Handbuch  der  Biochemischen  Arbeitsmethoden,"  V  (1912), 
1307-32. 

Other  references  on  micro-combustions:  Dubsky,  Chem.  Ztg.,  40  (1916), 
201-3;  Rinkes,  Chem.  Weekblad,  13  (1916),  800-3;  Fisceman,  Rend.  acad.  sci. 
(Napoli),  22  (1916),  31-8;  'and  Noorduijn,  "  An  electric  furnace  for  micro-ele- 
mentary analysis,"  Chem.  Weekblad,  14  (1917),  1131-5. 

2  Pregl  describes  the  Kuhlmann  balance  used  by  him  in  his  article  mentioned 
above.     See   also   Emich,   "  Micro-balances   and   their  application  in   chemical 
analysis,"  Naturwissenschafien,  3  (1915),  693-8. 

That  an  ordinary  sensitive  balance  can  be  used,  provided  the  investigator  can 
use  as  much  as  0.012-0.022  gram  of  substance,  has  been  shown  by  L.  E.  Wise, 
"  A  simplified  micro-combustion  method  for  the  determination  of  carbon  and 
hydrogen,"  Journ.  Amer.  Chem.  Soc.,  39  (1917),  2055. 

*Ber.,  46  (1913),  2574. 


222          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

Professor  Marie  Reimer,1  in  an  article  entitled,  "  On  Rapid 
Organic  Combustions/'  in  1915,  combined  the  good  points  of  the 
old  Liebig  method  and  of  Bekk's  method  and  showed  that  copper 
oxide  and  cerium  dioxide  could  be  used  together  advantageously 
for  the  rapid  determination  of  carbon  and  hydrogen.2  The 
technique  of  the  method  was  improved  by  Levene  and  Bieber.3 
The  copper  oxide  is  added  to  oxidize  any  products  of  incomplete 
combustion,  like  carbon  monoxide,  if  they  happen  to  get  beyond 
the  catalyst  or  in  case  the  supply  of  oxygen  is  momentarily 
used  up.  This  is  the  method  outlined  in  the  following  pages. 

The  use  of  alumina  4  as  the  absorbent  for  water  in  place  of  the 
time-honored  calcium  chloride  has  only  recently  been  described. 
It  is  believed  that  it  has  several  advantages  over  calcium  chloride, 
for  example:  (i)  it  is  a  better  absorbent  for  water,5  (2)  when  it 
has  absorbed  water  it  does  not  crystallize  and  "  freeze  "  to  the 
walls  of  the  absorption  bottle,  (3)  it  does  not  require  "  soaking  " 
with  C02  before  using,  and  (4)  the  same  bulk  of  material  has 
less  weight.  Its  chief  advantage  over  phosphorus  pentoxide  is 
that  it  does  not  liquefy  when  it  absorbs  water;  and  over  cone, 
sulfuric  acid,  that  it  is  a  solid  and  therefore  readily  handled 
and  produces  no  appreciable  back  pressure. 

In  the  general  description  which  follows,  it  is  assumed 
that  the  substance  to  be  analyzed  is  a  solid  and  contains  no 
other  elements  than  carbon,  hydrogen  and  oxygen.  Further  on, 
the  manner  of  dealing  with  substances  containing  in  addition 
nitrogen,  the  halogens,  sulfur,  phosphorus,  etc.,  is  discussed. 

Before  taking  up  the  method  in  detail  it  seems  not  inappro- 

1  Journ.  Amer.  Chem.  Soc.,  37  (1915),  1636-8. 

2  The  presence  of  the  copper  oxide  obviously  makes  it  impossible  to  estimate 
halogen  or  sulfur  at  the  same  time  as  the  carbon  and  hydrogen,  as  has  been  worked 
out  by  Dennstedt. 

3  Journ.  Amer.  Chem.  Soc.  40,  (1918),  460. 

4  Presented  by  the  author  at  the  Cleveland  meeting  of  the  American  Chemical 
Society,  September,  1918. 

5  That  is,  as  compared  with  the  ordinary  "  anhydrous  "  granular  calcium 
chloride.  Compare,  A.  T.  McPherson,  "  Granular  calcium  chloride  as  a  drying 
agent,"  Journ.  Amer.  Chem.  Soc.,  39  (1917),  1317-9;  and  Dover  and  Marden, 
"  A  comparison  of  the  efficiency  of  some  common  desiccants,"  ibid.,  39  (1917), 
1609.  Also  Baxter  and  Starkweather,  ibid.,  38  (1916),  2038. 


ORGANIC  COMBUSTIONS  223 

priate  to  give  the  following  quotation  from  Liebig's  original 
directions,  as  translated  by  Gregory: l 

"  The  essential  conditions  for  performing  a  good  analysis  are 
the  greatest  accuracy  in  weighing  and  the  strictest  conscientiousness 
in  the  execution  of  all  the  preparatory  steps  of  the  process.  Let 
us  not  flatter  ourselves  that  we  can  obtain  an  accurate  result  if  any- 
thing be  neglected  that  can  secure  it.  All  the  time  and  labor  we 
bestow  are  thrown  away,  if  we  omit  any  one  of  the  precautions  which 
are  recommended" 


II.  List  of  Apparatus  and  Chemicals  Required  for  the  Deter- 
mination of  Carbon  and  Hydrogen 

Apparatus 

1.  Electric  combustion  furnace  (p.  230). 

2.  Electric  pre-heater  (pp.  228-9). 

3.  Tank  of  oxygen  with  gauges  and  iron  stand  (p.  225). 

4.  Pyrex  combustion  tube,   76  cm.  long  and  15  mm.  inside 

diameter,  for  combustion  furnace  (pp.  231-2). 

5.  Pyrex  combustion  tube,  36  cm.  long  and  15  mm.  inside 

diameter,  for  pre-heater  (p.  228). 

6.  Asbestos  paper  for  lining  trough  of  the  furnace  and  of  the 

pre-heater  (pp.  229,  231). 

7.  Copper  gauze,  40  mesh,  i  square,  foot  (pp.  228,  235-6). 

8.  Copper  wire,  No.  16,  3  feet  long  (pp.  228,  235). 

9.  Bubble  counter  or  gas  bubble  indicator  (p.  227). 

10.  Six  red  rubber  stoppers,  one  holed;    four  of  them  size  i  or 

o,  depending  upon  diameter  of  combustion  tube;  and  two 
for  calcium  chloride  tube  connections  (pp.  228,  242,  245). 

11.  Rubber  pressure  tubing  (pp.  227,  230,  244). 

12.  Two  U- tubes,  with  ground -glass  stoppers,  12.5  cm.  (5  inches) 

(p.  229). 

13.  Two  Fisher  absorption  bottles  (new  style)  (p.  237). 

14.  One  calcium  chloride  tube,  as  a  guard  (p.  245). 

15.  One  small  bottle  for  palladious  chloride  solution  (p.  245). 

1 "  Instructions  for  the  Chemical  Analysis  of  Organic  Bodies  (1839),  3. 


224          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

16.  Glass  tube  for  palladious  chloride  bottle  (p.  245). 

17.  One  porcelain  or  quartz  boat  (p.  236). 

18.  One  special  weighing  tube,  boat  tube  ("  piggie  ")   (p.   251). 

19.  Two  quartz  dishes,  7.5  cm.  in  diameter  (p.  238),  or  one  large 

one  11.5  cm.  in  diameter,  depending  upon  conditions  for 
heating. 

20.  Crucible  tongs. 

21.  One  pair  of  pliers. 

22.  Desiccator. 

23.  Six  pine  splinters,  5  to  6  inches,  as  aids  in  rilling  and  empty- 

ing the  absorption  bottles  (pp.  240  (foot-note),  245). 

24.  One  pair  of  forceps  (long  and  narrow,  curved  near  the  end, 

somewhat  like  those  used  in  biological  work)  for  handling 
the  cotton,  and  for  use  in  rilling  and  emptying  the  absorb- 
tion  bottles  (p.  240). 

Chemicals 

1.  35  grams  soda  lime,  20  mesh,  2  per  cent  water  (about  one  fill- 

ing of  U-tube  (p.  229)  and  absorption  bottle)  (p.  243). 

2.  10  grams  soda  lime,  12  mesh,  15  per  cent  water  (about  one 

filling  of  absorption  bottle)  (p.  243). 

3.  100  grams  aluminium  chloride,  crystals  (AlCls.6H20)  (p.  238). 

4.  i  ounce  of  absorbent  cotton. 

5.  5  grams  cerium  nitrate  (p.  234). 

6.  120  cc.  pumice,  12  mesh  (pp.  234,  238). 

7.  One  vial  stop-cock  grease,  E.  &  A.  (p.  229). 

8.  Cone,  sulfuric  acid  for  bubble  counter  and  desiccator. 

9.  100  grams  cupric  oxide,  wire  form  (p.  236). 
10.  20  cc.  palladious  chloride  solution  (p.  245). 

III.  Topical  Outline  of  the  General  Method  of  Procedure 

1.  Set  up  the  electric  combustion  furnace  (p.  230). 

2.  Select  the  combustion  tube,  and  if  necessary  cut  to  proper 

length  and  "  round  "  the  edges  (p.  231). 

3.  Prepare  the  pumice  and  cerium  nitrate  mixture  and  place 

in  the  tube  (p.  234). 


ORGANIC  COMBUSTIONS  225 

4.  Get  ready  the  oxygen  apparatus,  pre-heater,  and  purifying 

train  (pp.  225-30). 

5.  Complete  the  preparation  of  the  cerium  dioxide  on  pumice 

in  the  tube  (pp.  234-5). 

6.  Prepare  the  guard  tube  for  protecting  the  combustion  tube 

when  the  absorption  train  is  not  attached  (pp.  246-7). 

7.  Prepare  the  rolls  of  copper  gauze  (p.  235),  the  copper  wire 

with  hook,  and  fill  the  remainder  of  the  combustion  tube 
(p.  236). 

8.  Make  the  preliminary  heating  ("  glowing  out  ")  (p.  246). 

9.  During  the  preliminary  heating,  prepare  the  entire  absorption 

train  (pp.  236-46). 

10.  Run  a  blank  determination  (p.    246),  and  weigh  out  the 

sample  of  dry  substance  (pp.  250-3). 

11.  The  combustion  proper  (p.  253). 

12.  Calculate  the  results  (p.  257). 

13.  Run  a  "  check  "  determination  (p.  256).  •+•• 

IV.  The  Apparatus  and  How  to  Put  it  Together  with  Notes 
on  Manipulation 

1.  Tank  of  Compressed  Oxygen  with  Stand  and  Pressure 
Gauges. — The  combustion  is  carried  out  in  oxygen,  which  is  most 
conveniently  supplied  in  a  tank  or  cylinder,  equipped  with  the 
usual  gauges,1  and  supported  in  an  iron  stand  (see  Fig.  14,  p.  226, 
and  Fig.  16,  p.  233).  The  large  gauge  registers  the  pressure 
in  the  cylinder  and  the  small  one  registers  the  pressure  at  which 
the  oxygen  is  delivered.  This  delivery  pressure  is  regulated  by 
means  of  a  thumbscrew  which  holds  a  spring  in  place  upon  an 
internal  diaphragm.  A  small  stop-cock  is  added  beyond  this 
gauge  in  order  that  the  gas  supply  can  be  regulated  further  or 
shut  off  quickly  when  necessary.  The  operating  pressure  is 
generally  from  i  to  4  pounds,  but  this  varies  greatly  with  the 
resistance  offered  throughout  the  combustion  system.  It  is 

1  While  this  book  is  being  published,  Prof.  S.  W.  Parr  has  described  "  A  needle 
valve  with  delicate  adjustment  for  high-pressure  gases,"  Journ.  Ind.  and  Eng. 
Chem.,  11  (1919),  768,  by  means  of  which  the  gas  can  be  delivered  directly  from  the 
cylinder  without  the  use  of  gauges. 


226         LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 


ORGANIC  COMBUSTIONS 


227 


regulated  in  accordance  with  the  gas  bubbling.  Ordinarily 
the  gas  bubbles  should  come  through  the  bubble  counter  so 
fast  that  they  can  just  be  counted,  about  three  to  four  a  second. 
This  rate  of  course  varies  with  the  substance  being  burned. 

2.  The  Bubble  Counter.1— The  bubble  counter  (Figs.  15  and 
1 6)  is  placed  next  to  the  supply  of  oxygen  and  is  connected  with 
the  outlet  from  the  pressure  gauges  by  means  of  heavy -walled  rub- 
ber pressure  tubing.  Only  a  very  small  amount  of  concentrated 
sulfuric  acid  is  required  in  this  apparatus,  usually  not  over  0.3  cc.2 
A  larger  amount  of  the  acid  gives  irregular  bubbling  on  account 


BUBBLE. 
COUNTER 


FIG.  15. 

of  the  depth  of  the  liquid.  The  liquid  is  run  in  through  a  small 
tube  or  dropped  into  the  outlet  tube  of  the  apparatus.  The 
apparatus  is  constructed  in  such  a  manner  that  this  small 
amount  of  sulfuric  acid  cannot  run  out,  even  though  it  be  turned 
upside  down,  and  cannot  flow  back  in  case  of  back  pressure.3 

1  Also  called  "  Gas  bubble  indicator." 

2  About  15  drops  as  counted  when  dropped  from  the  tip  of  a  small  tube,  drawn 
out  to  a  thin-walled  opening,  i  mm.  in  diameter,  such  as  would  be  used  for  filling 
the  apparatus. 

3  If  some  other  style  of  bubble  counter  is  used  which  is  not  so  constructed  that 
provision  is  made  for  possible  back  flow,  then  arrangements   should  be  made  for 
attaching  an  inlet  tube  containing  a  bulb  like  a  small  pipette  which  will  act  as  a 
reserve  reservoir  for  the  liquid  in  case  of  back  pressure. 


228          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

As  stated  in  connection  with  the  pressure  of  oxygen  under 
the  preceding  heading  the  rate  of  gas  bubbling  should  ordinarily 
be  so  fast  that  the  bubbles  can  just  be  counted,  three  to  four  a 
second,  although  this  rate  will  vary  more  or  less  with  different 
substances. 

The  object  of  the  bubble  counter  is  not  only  to  give  one 
an  idea  as  to  how  fast  the  gas  is  passing  into  the  apparatus, 
but  also  to  show  a  comparison  between  the  amount  of  gas  enter- 
ing the  train  and  the  amount  of  gas  leaving  the  system  through 
the  palladious  chloride  solution  (see  No.  5c,  p.  245).  This  will 
be  discussed  in  detail  later  (pp.  245,  254). 

The  bubble  counter  is  connected  with  the  glass  tube  in  the 
pre-heater  by  means  of  a  good  red  rubber  stopper.  On  the 
side  near  the  oxygen  tank  it  should  be  supported  with  a  clamp 
to  prevent  sagging  of  the  tube  in  the  pre-heater  when  it  is  hot. 
3.  Gas  Purifying  Apparatus,  including  the  Pre-heater.— 
The  Pre-heater. — The  compressed  oxygen  generally  contains 
small  amounts  of  impurities  and  it  has  been  found  that  it  is  best 
and  easiest  to  purify  it  by  passage  over  hot  copper  oxide  or  cerium 
dioxide  on  pumice  in  a  "  pre-heater  "  before  running  the  gas 
through  the  regular  drying  train.1  After  this  treatment  blank 
determinations  will  show  that  the  apparatus  is  ready  for  use  right 
after  the  preliminary  heating  of  the  combustion  tube.  Other- 
wise the  percentage^  of  hydrogen  will  be  too  high. 

Round  off  the  ends  of  a  Pyrex  combustion  tube,  36  cm. 
long  and  15  mm.  inside  diameter,  in  a  blast  flame.  Then  put 
inside  a  12  cm.  roll  of  copper  gauze  or  a  12  cm.  layer  of  copper 
oxide  in  wire  form.  The  roll  of  copper  gauze  or  copper  "  spiral  " 
as  this  is  sometimes  called,  is  made  by  tightly  rolling  a  piece 
of  copper  gauze  (40  mesh  to  the  square  inch),  12  cm.  wide  and 
about  1 8  cm.  long,  around  a  length  of  No.  16  2  copper  wire  arid 
bending  the  projecting  ends  of  the  wire  into  short  loops  close  to 
the  gauze. 

1This  has  been  found  necessary  when  the  oxygen  is  manufactured  by  electrolysis, 
as  demonstrated  in  our  laboratory  by  Miss  Alice  R.  Thompson.  It  contains 
small  amounts  of  hydrogen  (0.3  to  i.o  per  cent). 

2  Brown  &  Sharpe  gauge. 


ORGANIC  COMBUSTIONS  229 

This  tube  is  heated  to  dull  redness  in  a  20  cm.  (8  in.)  electric 
furnace  provided  for  this  purpose.  It  consists  of  one  of  the 
sections  of  an  electric  combustion  furnace,  mounted  like  the  regu- 
lar furnace  itself,  with  trough  and  its  own  rheostat  for  tempera- 
ture control.  In  order  to  prevent  the  glass,  if  it  should  melt, 
from  adhering  to  the  trough,  place  under  it  a  strip  of  asbestos 
paper.  The  ends  of  the  glass  tube  are  allowed  to  project  more 
than  usual  beyond  the  furnace,  since  all  precautions  must  be 
taken  to  prevent  the  rubber  stoppers  from  burning. 

The  Purifying  Train. — The  oxygen  must  be  freed  from  any 
possible  traces  of  carbon  dioxide  and  water,  and  therefore  it  is 
next  passed  through  a  12.5  cm.  (5  in.)  U-tube l  containing 
soda  lime  (2o-mesh  size  and  containing  2  per  cent  of  moisture) 
and  then  through  another  U-tube  containing  alumina-pumice.2 
These  U-tubes  should  be  fitted  with  ground  glass  stoppers  3  and 
should  have  glass  braces4  to  give  strength  and  to  prevent 
breakage.  The  stoppers  must  be  greased  with  a  good  stop- 
cock grease  5  in  such  a  way  that  they  present  a  clear  surface 
showing  good  contact.  Too  little  grease  makes  a  stopper  stick 
or  leak;  too  much  often  stops  up  the  openings  and  also  makes 
the  stopper  so  loose  that  the  gas  pressure  may  force  it  out  of 
the  tube.  Never  turn  a  stop-cock  by  using  only  one  hand. 
Use  the  other  hand  at  the  same  time  to  hold  the  U-tube,  then 
you  can  be  sure  that  the  stopper  is  in  tight  and  that  there  are 
no  channels.  The  stoppers  should  be  kept  closed  when  the 
apparatus  is  not  in  use.  This  applies  particularly  to  the  alumina- 
pumice  U-tube. 

1 A  small  funnel  of  thin  glass  with  a  wide  stem  is  very  useful  in  filling  the 
apparatus. 

2  See  p.  238  for  preparing  the  alumina-pumice. 

3  Fasten  these  stoppers  loosely  with  wire  or  twine,  otherwise,  if  excessive 
pressure  is  developed,  they  may  be  forced  out  and  the  stoppers  broken.    This 
causes  much  inconvenience.     Do  not  use  rubber  bands.     On  account  of  their 
elasticity  they  often  alter  the  position  of  the  stopper  after  it  has  been  set. 

4  R.  Nowicki,  Chem.  Ztg.,  28  (1904),  622;  Mclntire,  Journ.  Amer.  Chem.  Soc., 
33  (1911),  450-1  (like  the  ones  shown  in  the  figure).      For  other  similar  types, 
see  Abderhalden's  "  Handbuch  der  Biochemischen  Arbeitsmethoden,"  VIII  (1915), 
400-1. 

5  Do  not  use  vaseline,  since  the  stoppers  are  likely  to  stick.     Eimer  &  Amend, 
N.  Y.,  furnish  a  good  stop-cock  grease  in  handy  soft  metal  tubes. 


230          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

Place  a  wad  of  absorbent  cotton  on  top  of  the  material  in 
each  arm  of  the  U-tubes  to  keep  the  stop-cocks  free  from  dust 
particles. 

Connect  the  U-tubes  by  means  of  rubber  pressure  tubing. 
It  is  well  to  support  these  U-tubes  by  means  of  a  clamp  around 
the  rubber  connection.  This  prevents  any  sagging  of  the  tubes 
in  both  pre-heater  and  combustion  furnace  when  they  are  hot. 

The  preparation  of  the  aluminium  oxide  on  pumice  is  de- 
scribed in  connection  with  the  absorption  bottle  for  water 
(see  5a,  p.  238).  The  same  kind  of  material  must  be  used  here 
for  drying  the  gas  as  is  used  for  absorbing  the  water  in  the 
absorption  train,  otherwise  there  will  be  discrepancies  in  the 
percentage  of  hydrogen.1 

Instead  of  the  U-tubes  any  variety  of  absorption  apparatus 
may  be  used.  No  weighing  is  necessary  and  therefore  the  shape 
does  not  require  consideration.  The  same  type  of  absorption 
bottles  as  described  in  the  absorption  train  can  be  used  if  desired. 

If  many  combustions  are  to  be  run,  the  purifying  train 
should  consist  of  more  U-tubes,  or  of  larger  apparatus  according 
to  conditions. 

4a.  The  Electric  Combustion  Furnace. — The  multiple  unit 
type  of  electric  combustion  furnace  is  the  most  convenient  to 
use.2  Each  heating  section  is  regulated  by  its  own  rheostat 
placed  underneath  and  is  fitted  with  replaceable  heating  units. 
The  upper  part  of  each  section  can  be  lifted  and  the  tube  ex- 
amined at  any  time  during  the  course  of  the  combustion.  The 
maximum  current  requirement  is  from  12  to  18  amperes,  de- 
pending upon  the  model.  The  units  are  so  well  insulated  that 
parts  of  the  tube  may  be  heated  to  redness  while  other  parts 
remain  cool  fairly  close  to  the  unit.  This  insulation  to  prevent 
loss  of  heat  is  a  boon  to  the  manipulator  also  because  it  makes  it 
possible  to  run  combustions  in  a  small  room  even  in  summer  time 

1  See,  also,  Morse,  "  Exercises  in  Quantitative  Chemistry"  (1905),  PP-  340-2, 
353-4,  where  data  are  given  to  illustrate  the  difference  in  the  absorption  capacity 
of  warm  and  of  cold  calcium  chloride,  and  of  cone,  sulfuric  acid. 

.  2  Multiple  unit  electric  organic  combustion  furnace,  Type  122-8,  manufactured 
by  the  Electric  Heating  Apparatus  Co.,  Newark,  N.  J.,  is  built  in  accordance  with 
the  specifications  given  in  this  description. 


ORGANIC  COMBUSTIONS  231 

with  no  more  discomfort  than  in  carrying  out  ordinary  work. 
The  trough  for  supporting  the  combustion  tube  is  made  of  nickel 
and  therefore  it  does  not  corrode  appreciably  even  in  the  high 
heat.  A  strip  of  asbestos  paper  is  placed  in  this  trough  and  then, 
if  the  glass  melts,  it  will  not  stick  to  the  metal  and  crack  on 
cooling.  In  case  the  tube  does  crack,  turn  off  the  current  and 
when  the  furnace  is  cold  remove  any  copper  oxide  wire  that  might 
get  among  the  wires  of  the  heating  units  when  the  glass  is 
taken  away,  otherwise  short  circuits  will  result  later. 

The  electric  combustion  furnace  is  ordinarily  supplied  with 
three  heating  sections  of  unequal  lengths.  Each  of  these  can 
heat  the  tube  to  redness.  The  longest  section  (No.  2)  l  should 
be  in  the  center.  The  heat  regulation  of  the  smallest  -section 
(No.  i)  should  be  such  that  when  the  current  is  on  and  all  resist- 
ance in,  the  temperature  should  not  be  above  4o°-5o°.  When 
necessary,  it  should  be  possible  to  keep  the  section  of  medium 
length  (No.  3)  at  3OO°-32o°,  since  this  is  the  temperature 
required  when  the  lead  peroxide  mixture  is  used  in  the  combustion 
of  substances  containing  nitrogen  and  sulfur.  (See  p.  265.) 

Each  rheostat  is  generally  arranged  in  such  a  way  that 
when  the  handle  is  at  the  right  all  the  resistance  is  in  and  there- 
fore this  position  gives  the  lowest  temperature.  The  heat  is 
increased  by  moving  the  handle  toward  the  left.  . 

The  temperature  must  be  carefully  watched  when  the  coils 
of  wire  are  red,  since  it  gradually  rises  and  thus  may  cause  the 
tube  to  melt  after  a  time.  In  a  well-lighted  room  it  is  dif- 
ficult to  tell  the  temperature  by  the  color  of  the  wires.  How- 
ever, if  you  lift  the  upper  half  just  a  little  so  that  the  inside 
is  shaded,  you  can  then  obtain  a  good  idea  of  the  color  and  be 
able  to  judge  the  temperature  properly. 

The  handles  on  the  upper  section  should  be  wound  with 
asbestos  cord  to  make  it  possible  to  touch  them  with  the  ringers 
at  any  time.  A  piece  of  heavy  white  rubber  tubing  serves  well 
in  place  of  the  asbestos  cord. 

4b.  The  Combustion  Tube  and  How  to  Fill  It. — For  combus- 
tion tubing,  Pyrex  glass  is  generally  better  than  Jena  or  Bo- 

1  The  sections  are  numbered  correspondingly  on  the  diagram,  Fig.  16,  p.  233. 


232          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

hemian  glass  since  it  does  not  vitrefy  and  become  opaque  at  the 
required  high  temperature.1  Select  a  combustion  tube  of  15  mm. 
inside  diameter  and  of  such  a  length  (about  76  cm.)  that  it  will 
extend  3-4  cm.2  beyond  the  ends  of  the  nickel  trough.3  Usually 
this  amount  of  extension  is  sufficient  to  prevent  the  burning  of 
the  rubber  stoppers.  The  end  next  to  the  absorption  train  should 
not  be  so  long  that  much  water  can  condense  since  it  is  difficult 
to  drive  this  water  through. 

Round  off  the  edges  of  the  tube  by  gentle  heating  first  and 
then  with  a  blast  flame,  so  that  they  will  not  cut  the  rubber 
stoppers.  Do  not  change  the  bore  of  the  tube ! 

Clean  the  combustion  tube,  and  fill  it  as  indicated  in  the 
diagram,  Fig.  16,  making  sure  that  the  positions  of  the  materials, 
etc.,  are  in  proper  relation  to  the  sections  of  trie  furnace.  The 
dimensions  given  are  for  the  72  cm.  (283  in.)  furnace.  Even 
if  a  longer  furnace  is  used,  the  positions  of  the  cerium  dioxide 
and  the  boat  should  be  relatively  the  same  as  described  here, 
the  extra  length  being  taken  up  simply  with  more  copper  oxide 
wire. 

1  Where  many  combustions  are  to  be  run,  a  quartz  tube  with  a  transparent 
section  where  the  boat  is  placed  is  both  advantageous  and  economical.    Levene 
and  Bieber,  Journ.  Amer.  Chem.  Soc.,  40  (1918),  460. 

2  A  longer  extension  is  necessary  when  a  gas  furnace  is  used. 

3  Pyrex  combustion  tubing  is  cut  with  a  narrow  grinding  wheel.     The  ordinary 
methods  cannot  always  be  used,  since  the  expansion  of  the  glass  on  heating  is  so 
small.     Some  of  these  methods,  however,  do  work  sometimes  and  are  given  here 
for  sake  of  convenience. 

1.  Make  a  short  file  mark  at  the  desired  length  and  then  heat  the  tube  at  this 
point  by  giving  a  piece  of  twine  two  turns  at  the  mark  and  drawing  the  twine  up  and 
down  rapidly  several  times  while  the  tube  is  held  securely  by  another  person  on  the 
desk  with  the  edge  for  a  guide.     Then  immediately  put  the  tube  under  cold  water, 
or  apply  a  wet  cloth. 

2.  A  second  method  of  cutting  the  glass  tube  is  to  make  the  file  mark  as  above 
and  then  heat  this  mark  very  carefully  with  the  slanting  tiny  flame  from  a  capil- 
lary tube.     This  tube  can  be  made  of  glass,  although  a  metal  one  is  of  course  pref- 
erable.    As  soon  as  a  crack  is  formed  follow  it  with  the  tiny  flame  until  it  extends 
clear  around.     Do  not  point  the  flame  directly  at  the  tube,  always  slant  it,  other- 
wise the  crack  may  extend  longitudinally.1 

3.  Another  method  consists  in  winding  a  platinum  or  ni chrome  wire  around 
the  tube  and  then  heating  it  to  redness  by  means  of  an  electric  current. 

1  K.H.  Parker,  Journ.  Amer.  Chem.  Soc.,  40  (1918),  195,  described  "Anew  glass  cut- 
ting tool," — a  small  gas-heated  iron  for  which  he  claims  excellent  results. 


ORGANIC  COMBUSTIONS 

n 

e 


233 


234          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

Prepare  the  cerium  dioxide  first.  Use  enough  pumice  l  of 
i2-mesh  size  to  fill  5-6  cm.  of  the  tube.  Dissolve  5  grams  of 
pure  white  crystals  of  cerium  nitrate  in  enough  water  (about 
1 2  cc.)  to  cover  the  pumice  in  a  quartz  or  porcelain  dish.  Evapo- 
rate this  mixture  to  dryness  on  the  steam-bath,  with  frequent 
stirring  to  prevent  formation  of  a  cake.  Then  transfer  this 
impregnated  pumice  to  the  tube  and  put  the  asbestos  wads  in 
place  by  means  of  a  long  glass  rod  flattened  at  one  end.  The 
asbestos  wads  should  not  be  over  0.5  cm.  in  width,  and  the 
asbestos  must  not  be  so  tightly  packed  that  the  oxygen  gas  will 
not  go  through  it.  This  can  be  remedied  when  it  is  in  place  by 
putting  in  tiny  holes,  if  necessary,  with  a  long  glass  rod  drawn 
out  to  a  point.  Support  the  asbestos  wads  in  position  by  using 
a  roll  of  copper  gauze,  o.  5  cm.  in  width.  This  prevents  them  from 
crumbling  and  from  being  moved  out  of  position  by  the  force 
of  the  gas,  etc.  It  is  important  for  proper  heating  that  the 
cerium  dioxide  be  placed  in  the  relative  position  shown  in  the 
diagram  (C)  and  also  that  the  end  of  the  boat  be  not  more  than 
2.5  cm.  distant,  in  order  to  prevent  the  formation  of  explosive 
mixtures  of  gases.  Therefore  the  size  of  the  asbestos  wad  and 
the  short  rolls  of  copper  oxide  gauze  must  not  be  greater  than 
mentioned  above.  Complete  the  drying  by  heating  the  tube 
at  a  low  temperature  and  at  the  same  time  passing  a  current  of 
pure  dry  oxygen  through  the  tube.  As  soon  as  no  more  mois- 
ture collects  in  the  cool  end  of  the  tube  gradually  raise  the  tem- 
perature while  the  oxygen  is  still  passing  and  finally  complete 
the  decomposition  of  the  cerium  nitrate  at  dull  red  heat.2 
Allow  to  cool  in  the  current  of  dry  oxygen  or  attach  a  drying 
tube  to  the  open  end  of  the  combustion  tube.  When  hot,  the 

1  Pumice  is  used  instead  of  asbestos,  then  the  material  does  not  crumble  and 
"  sag."     Fisher  and  Wright,  Journ.  Amer.  Chem.  Soc.,  40  (1918),  869. 

2  This  procedure  is  used  in  accordance  with  the  suggestion  of  Levene  and 
Bieber,  Journ.  Amer.  Chem.  Soc.,  40  (1918),  460,  who  found  that  when  the  decom- 
position was  carried  out  over  a  gas  burner  the  oxide  was  not  always  so  good  a 
catalyst  as  when  prepared  as  above. 

If  the  material  is  heated  too  much  at  first  some  of  it  is  driven  out  of  the  pumice 
and  deposited  upon  the  inner  walls  of  the  tube,  where  it  will  remain  when  dry  and 
form  an  opaque  layer.  No  special  harm  is  done  if  this  happens. 


ORGANIC  COMBUSTIONS  235 

cerium  dioxide  is  deep  yellow,  but  this  color  changes  to  a  straw 
yellow  when  the  material  is  cold.  Complete  the  preparation  of 
the  cerium  dioxide  before  putting  any  of  the  other  substances 
into  the  tube.  Otherwise  the  copper  nitrate  which  is  formed 
may  cause  trouble  later  by  slowly  being  decomposed  and  giving 
off  oxides  of  nitrogen  which  are  caught  in  the  absorption  train. 
The  small  rolls  of  gauze  next  to  the  asbestos  need  not  be  con- 
sidered in  this.  Once  the  cerium  dioxide  has  been  prepared 
it  will  remain  ready  for  use  at  any  time  provided,  of  course,  that 
the  combustion  tube  is  kept  stoppered  when  not  in  use. 

For  position  A  prepare  a  roll  of  copper  oxide  gauze,  8  cm. 
long,  by  rolling  a. piece  of  copper  gauze  (40  mesh  to  the  square 
inch),  8  cm.  wide  and  about  18  cm.  long,  around  a  length  of 
No.  1 6  copper  wire  (B.  &  S.  gauge)  and  bending  the  short 
projecting  ends  of  the  wire  into  short  loops  close  to  the  gauze. 
It  should  be  rolled  tightly.  Let  it  remain  in  the  tube  overnight 
if  possible  and  become  molded  to  the  proper  shape  and  size. 
When  oxidized  it  should  fit  the  tube  snugly  but  not  so  snugly 
that  it  sticks  and  cannot  readily  be  withdrawn.  After  it  has 
remained  in  the  tube  overnight  cut  off  some  of  the  gauze  if 
necessary.  The  gauze  usually  is  covered  with  more  or  less 
grease  and  dirt  and  if  directly  oxidized  in  the  tube  the  inner 
walls  of  the  glass  often  become  coated  with  a  black  layer  of 
fine  copper  oxide  which  makes  the  tube  opaque.  Therefore  it 
is  best  to  oxidize  the  roll  of  gauze  (or  copper  "  spiral  "  as  it  is 
sometimes  called)  in  a  large  blast  flame  or  over  a  Meker  burner, 
before  heating  it  in  the  tube. 

The  copper  oxide  gauze  is  moved  back  and  forth  in  the  tube 
by  means  of  a  stout  copper  wire  with  a  short  hook  bent  at  right 
angles. 

The  object  of  this  roll  of  gauze  is  twofold:  In  the  first  place 
it  acts  as  an  "  oxidation  buffer,"  that  is,  it  oxidizes  any  gases 
that  may  go  backward,  and  thus  prevents  them  from  getting 
so  far  back  that  the  determination  is  spoiled.  Furthermore,  by 
its  very  shape,  size,  and  position  it  causes  the  oxygen  to  flow 
through  its  interstices  more  rapidly  than  in  the  open  spaces 
of  the  tube  before  and  after  and  in  this  way  tends  to  keep  any 


236          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

unoxidized  gases  which  may  go  backward  from  getting  beyond  it 
before  they  are  completely  oxidized. 

The  intervening  space  of  12  cm.  between  the  roll  of  gauze 
at  A  and  the  cerium  dioxide  at  C  is  reserved  for  the  boat  B. 
As  stated  above  (p.  234),  the  boat  should  be  placed  within  about 
2.5  cm.  of  the  cerium  dioxide.  A  greater  distance  will  allow  the 
formation  of  explosive  mixtures  of  oxygen  and  the  gases  from  the 
substance. 

Ordinarily  a  porcelain  or  quartz  boat  7  cm.  long  is  used. 
Clean  it  with  dilute  nitric  acid,  heat  in  a  blast  flame  and  allow 
to  cool  in  a  desiccator.  A  longer  boat  is  used  for  very  light 
and  fluffy  materials.  A  boat  with  little  compartments  aids 
the  burning  of  a  substance  which  decomposes  readily.  The 
compartments  prevent  that  portion  of  the  substance  that  has 
melted  from  mixing  with  the  unmeited  portion. 

For  weighing  out  sample,  see  p.  250. 

Beyond  the  cerium  dioxide  in  space  D  put  a  23  cm.  layer  of 
cupric  oxide  1  in  wire  form  and  keep  it  in  place  with  a  short  roll 
of  copper  oxide  gauze  E.  Cupric  oxide  is  very  hygroscopic. 

The  i2-cm.  space  at  F  is  reserved  for  the  lead  peroxide 
mixture  which  is  used  when  substances  containing  nitrogen  and 
sulfur  are  burned.  (See  p.  265.)  Otherwise  it  may  be  filled 
with  copper  oxide  wire. 

5.  The  Absorption  Train. — The  absorption  train  is  made  up 
of  two  absorption  bottles,  the  first  one  for  collecting  the  water 
and  the  second  one  for  the  carbon  dioxide,  and  a  guard  tube  and 
bottle  of  palladious  chloride  solution.  The  absorption  apparatus 
selected  should  be  one  that  is  capable  of  being  readily  and 
thoroughly  cleaned,  easily  filled  and  emptied,  handled  without 
difficulty,  of  a  moderate  capacity,  and  when  filled  not  weighing 
over  100  grams.  For  carbon  dioxide  absorption,  it  should  have 
two  chambers  which  can  be  entirely  shut  off  one  from  the  othei 
when  the  apparatus  is  not  in  actual  use.  It  is  believed  that  th< 

1  Cupric  oxide  which  has  been  used  in  the  determination  of  nitrogen  cannot 
be  used  for  carbon  and  hydrogen  since  it  contains  some  carbon  dioxide,  unless  it 
has  been  heated  for  several  hours  in  a  stream  of  oxygen  or  in  the  open  air.  Com- 
pare foot-note,  p.  284. 


ORGANIC  COMBUSTIONS  237 

absorption  bottle  1  shown  in  Fig.  17,  fulfills  these  requirements. 


{4  mm. 


Dotted  Lines 

Indicate  Ground 

Surfaces  of  Dottle 


FIG.  17. — Fisher  Absorption  Bottle. 

1  Fisher,  U.  S.  Patent  1,313,626  (1919).  The  bottle  is  manufactured  by  Eimer 
&  Amend,  New  York.  The  forerunner  of  this  particular  bottle  had  no  means  of 
shutting  off  the  two  chambers,  and  the  stopper  was  ground  in  to  fit  the  top  of  the 
inner  standing  tube  instead  of  the  bottom.  See  Fisher,  "  A  new  form  of  absorp- 
tion bottle  for  use  with  either  calcium  chloride  or  soda  lime  in  the  elemental  anal- 
ysis of  carbon  and  hydrogen  in  organic  substances,"  Journ.  Ind.  and  Eng.  Chem. 
8  (1916),  368. 

Other  forms  of  absorption  bottles  and  tubes  can  be  found  in  the  apparatus 
catalogues. 


238          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

The  bottle  is  literally  a  U-tube  turned  partially  inside  out. 
The  available  capacity  of  the  stopper  and  its  extension  tube 
is  25  cc.,  and  of  the  outer  chamber  of  the  bottle,  25-30  cc., 
making  a  total  available  capacity  of  50-55  cc.  By  way  of 
comparison  it  is  of  interest  to  note  that  an  ordinary  5 -inch 
U-tube  has  a  total  available  capacity  of  only  20-25  cc- 

a.  The  First  Absorption  Bottle. — Aluminium  oxide  (alum- 
ina) is  used  for  absorbing  the  water  formed  in  the  combustion. 
It  is  mixed  with  pumice  to  make  it  more  porous.  The  use  of 
alumina  is  described  first.  Following  this,  on  p.  239,  is  a  de- 
scription of  the  use  of  calcium  chloride  for  the  absorption  of 
water.  It  should  be  borne  in  mind  that  whatever  absorbing 
agent  for  water  is  used  here,  the  same  one  must  also  be  used 
in  the  soda  lime  bottle  and  in  the  drying  train  (compare  p.  230). 

Preparation  of  Aluminium  Oxide  (Alumina)  for  the  Absorp- 
tion Bottle. — Dissolve  50  grams  of  hydrated  aluminium  chloride 
(AlCl3-6H20)  in  100  cc.  of  warm  water  in  a  11.5  cm.  quartz 
or  porcelain  dish  and  stir  in  50  cc.  (about  24  grams)  of  i2-mesh 
pumice.1  Boil  down  this  mixture  over  a  wire  gauze  or  asbestos 
disk  with  a  free  flame.  Stir  well  with  a  stout  glass  rod  after 
most  of  the  water  has  disappeared,  since  it  foams  a  good  deal 
and  will  also  form  a  cake.  The  particles  of  pumice  should  be 
kept  separated  as  far  as  possible.  Continue  the  heating  and 
stirring  until  there  is  no  danger  of  later  fusion  of  the  hydrated 
salt  and  agglomeration  of  the  small  lumps  of  impregnated  pumice. 
Transfer  this  material  to  a  7.5  cm.  quartz  or  porcelain  dish  and 
heat  in  an  electric  muffle  furnace  to  700°-;  50°  2  until  no  more 
hydrogen  chloride  is  given  off.  A  higher  temperature  should  not 
be  used.  The  time  can  be  shortened  to  thirty  to  forty-five  min- 
utes if  a  stream  of  air  is  blown  or  drawn  through  the  heating 

1  These  amounts  are  for  the  first  absorption  bottle.     Double  them  or  make  up 
a  second  batch  in  order  to  have  enough  for  all  requirements.     On  account  of  the 
foaming,  the  evaporation  is  best  done  in  this  larger  dish.     The  final  heating  can 
also  be  done  in  this  same  dish,  but  it  is  too  large  for  the  ordinary  muffle  furnace, 
which  has  an  opening  only  10  cm.  wide. 

2  Approximately  these  same  conditions  can  be  obtained  by  heating  the  mixture 
in  the  dish  on  a  nichrome  gauze  at  the  tip  of  a  non-luminous  flame  5  cm.  high,  far 
i^  to  2  hours. 


ORGANIC  COMBUSTIONS  239 

chamber  to  remove  the  gaseous  products.  Traces  of  hydrogen 
chloride  can  of  course  be  detected  with  the  nose  or  by  means  of 
ammonium  hydroxide.  At  the  end  of  the  heating  the  dishes 
should  be  cooled  in  a  desiccator  which  has  no  other  substance 
in  it.  A  vacuum  desiccator  is  convenient  to  use  since  the  pres- 
sure inside  from  the  heated  atmosphere  can  be  released  with 
the  stop-cock.  If  the  heating  is  too  long  or  too  high  the  alumina 
will  no  longer  cling  to  the  pumice,  but  will  drop  off  as  a  fine 
powder.  It  will  do  this  to  some  extent  under  any  conditions. 
According  to  Johnson  l  the  alumina  is  an  excellent  drying 
agent  up  to  the  time  that  it  has  absorbed  about  18  per  cent 
of  its  weight  of. water  at  ordinary  temperature.  Fifty  grams  of 
hydrated  aluminium  chloride  theoretically  yields  about  10.7 
grams  of  aluminium  oxide,  and  this  amount  ought  to  absorb 
about  1.92  grams  of  water  under  ideal  conditions.  If  we  con- 
sider the  average  organic  substance  as  containing  about  5  per 
cent  of  hydrogen,  then  a  0.2  gram  sample  will  yield  approximately 
0.09  gram  of  water,  and  on  this  basis  the  aluminium  oxide  theo- 
retically ought  to  suffice  for  twenty-one  combustions.  In  prac- 
tice the  mixture  can  safely  be  used  for  four  to  five  combustions. 

NOTE. — Originally  the  author  used  asbestos  instead  of  pumice  in  order  to 
give  plenty  of  surface,  and  prepared  the  reagent  by  heating  10  grams  of  pure 
aluminium  hydroxide  with  2  grams  of  asbestos,  as  described  above.  The  aluminium 
hydroxide  must  be  free  from  alkali.  When  mixed  with  neutral  water  it  should  give 
only  the  faintest  color  with  phenolphthalein  (compare  curve  on  p.  1500  in  article 
by  Blum,  "  The  Constitution  of  Aluminates,"  Journ.  Amer.  Chem.  Soc.,  35  (1913)). 
The  alumina-asbestos  mixture  is  very  efficient  as  shown  in  this  laboratory  by 
Mr.  Henry  L.  Faust,  but  it  packs  very  readily  and  then  it  requires  three  to  four 
hours  for  the  complete  passage  of  carbon  dioxide  through  it,  in  some  cases.  The 
material  can  be  regenerated  by  re-heating,  but  after  a  time  the  asbestos  crumbles 
to  a  powder.  Pumice  was  being  considered  in  place  of  the  asbestos  when  Mr. 
Geo.  H.  Walden  suggested  the  use  of  hydrated  aluminium  chloride  as  the  source 
of  alumina  instead  of  the  aluminium  hydroxide. 

The  Use  of  Calcium  Chloride.  Calcium  chloride  should  be  in 
a  granular  porous  form  (size  about  8-mesh)  and  free  from  dust 
particles,  when  used  in  the  absorption  train.  The  ordinary 
"  anhydrous "  material  as  obtained  on  the  market  can  be 
made  much  more  efficient  by  heating  it  to  26o°-275°  in  a  current 
1  Journ.  Amer.  Chem.  Soc.,  34  (1912),  911-2. 


240          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

of  air  dried  over  phosphorus  pentoxide.1  Even  this  porous 
material,  however,  which  contains  some  surface  moisture,  is 
better  than  the  fused  calcium  chloride.  Calcium  chloride  gen- 
erally contains  basic  substances  and  these  absorb  carbon  dioxide. 
On  that  account  it  must  be  saturated  while  in  the  absorption 
bottle  with  carbon  dioxide  by  passing  a  stream  of  the  dry  gas 
through  it  for  two  hours  and  then  displacing  this  with  dry  air 
or  oxygen.  Or,  better,  after  driving  out  all  the  original  air 
with  dry  carbon  dioxide  (one-half  hour),  let  it  stand  overnight, 
and  then  displace  the  gas  with  dry  air  or  oxygen.2 

The  amount  of  moisture  absorbed  by  calcium  chloride  varies 
with  the  temperature  even  around  the  temperature  of  ordinary 
working  conditions.3  This  is  sometimes  very  important  since 
the  temperature  of  the  calcium  chloride  in  the  drying  train  is 
seldom  the  same  as  that  of  the  calcium  chloride  in  the  absorption 
train. 

To  fill4  the  absorption  bottle:  Remove  the  stopper  and  its 
extension  tube.  Place  a  flat  wad  of  cotton  over  the  hole  in 
the  inside  of  the  stopper5  and  rapidly  fill  the  stopper  and  its 
extension  tube  with  some  of  the  alumina-pumice.  Put  in  a  plug 
of  absorbent  cotton  near  the  end.  Place  this  filled  part  of  the 
bottle  immediately  into  a  desiccator  over  fresh  cone,  sulfuric  acid. 
Without  any  delay,  put  some  cotton  at  the  bottom  of  the  outer 

1  A.  T.  McPherson,  "  Granular  Calcium  Chloride  as  a  Drying  Agent,"  Journ. 
Amer.  Chem.  Soc.,  39  (1917),  1317-9. 

2  Morse,  "  Exercises  in  Quantitative  Chemistry  "  (1905),  340,  354,  states  that 
these  methods  are  open  to  objections  since  the  conversion  into  the  carbonate  is 
only  superficial,  and  when  the  moisture  comes  in  new  surfaces  are  exposed.    He 
also  states  that  calcium  chloride  may  be  obtained  in  a  neutral  condition,  that  is, 
free  from  oxide,  by  evaporating  a  solution  of  the  chloride  with  ammonium  chloride 
and  heating  the  residue  until  the  latter  salt  has  been  expelled. 

3  Morse,  ibid.,  340-1. 

4  A  long  narrow  pair  of  forceps  with  slightly  curved  ends,  such  as  are  used  in 
biological  work,  and  a  pine  splinter,  will  be  found  very  convenient  as  aids  in  filling 
and  also  emptying  the  bottle.     The  pine  splinter  is  used  instead  of  a  piece  of  metal 
since  a  scratch  on  the  inside  of  the  bottle  will  almost  invariably  cause  a  crack. 
Similarly  a  glass  rod  with  a  sharp  end  should  not  be  used.     If  a  wire  is  used,  be 
sure  that  the  end  is  protected  with  cotton. 

6  But  do  not  fill  the  entire  stopper  with  cotton,  since  the  space  is  needed  for  the 
drying  agent. 


ORGANIC  COMBUSTIONS  241 

chamber  of  the  main  part  of  the  bottle  to  keep  particles  from 
sifting  through  the  holes  and  getting  upon  the  ground  surface. 
Insert  a  plug  of  cotton  or  a  cork  in  the  top  of  the  inner  standing 
tube  in  the  center  of  the  bottle,  and  then  quickly  fill  the  outer 
chamber  with  the  alumina-asbestos  mixture.  Pack  in  some 
cotton  above  it  near  the  top  of  the  tube.  This  keeps  the  fine 
particles  from  getting  upon  the  ground  surfaces  of  the  stopper 
and  also  from  being  blown  out  into  the  side  arm.  Take  out  the 
cotton  or  cork  from  the  top  of  the  inner  standing  tube,  quickly 
remove  all  dust  particles  from  the  ground  surfaces  in  the  bottom 
of  the  bottle  and  at  the  top  by  means  of  cotton  held  in  the 
forceps,  carefully  grease  with  a  good  stop-cock  grease l  and 
insert  the  stopper.  Do  not  use  vaseline,  since  it  has  no  "body" 
and  is  too  "  thin,"  and  causes  sticking  of  the  stopper.  The 
ground  surfaces,  when  properly  greased,  will  appear  clear,  show- 
ing that  the  joints  are  gas  tight.  Great  care  should  be  used  in 
greasing  the  lower  ground  joint.  Too  little  grease  will  make  it 
stick  and  too  much  may  close  the  holes.  If  this  ground  joint 
becomes  "  frozen  "  there  is  little  hope  of  being  able  to  open  the 
bottle.  Keep  the  cotton  from  coming  in  contact  with  the 
ground  surfaces. 

This  bottle  ought  to  be  provided  with  a  small  ground  stopper  2 
in  one  arm,  and  this  arm  is  the  one  that  is  next  to  the  combustion 
tube.  Then  when  the  combustion  is  over  and  the  rubber  stopper 
removed,  the  ground  stopper  is  inserted  and  any  water  that  may 
remain  in  the  arm  cannot  evaporate  during  further  manipula- 
tions. Only  a  very  small  amount  of  grease,  if  any,  should  be 
put  on  this  stopper  on  account  of  the  danger  of  rubbing  it  off 
and  thus  causing  loss  of  weight. 

The  side  arms  of  the  bottle  are  bent  slightly  upward  near 


1  See  footnote,  p.  229. 

2  In  case  the  absorption  bottle  is  not  provided  with  a  small  ground  stopper, 
attach  a  short  piece  of  rubber  tubing  and  plug  up  the  open  end  with  a  piece  of 
glass  rod.     This  serves  to  prevent  the  evaporation  of  any  moisture  that  may 
remain  in  the  arm.     Since  the  rubber  may  vary  in  weight  under  the  different 
conditions  of  treatment  it  should  be  removed  and  the  arm  carefully  cleaned  before 
the  bottle  is  weighed 


242          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

the  neck  in  order  that  any  droplets  of  water  that  may  collect  will 
remain  in  the  depression  and  not  tend  to  run  along  the  arm 
during  subsequent  handling.  The  side  arms  should  be  free  from 
any  dust  particles  which  might  be  lost  during  the  operation 
and  change  the  weight.  The  cotton  inside  the  bottle  is  used 
partly  to  prevent  any  particles  from  being  carried  by  the  gas 
into  these  side  arms. 

Connect  the  arm  prepared  for  the  small  stopper  directly  with 
the  combustion  tube  by  means  of  a  good  rubber  stopper.1  In 
doing  this  do  not  grasp  the  bottle  itself — take  hold  only  of  the 
side  arm.  Otherwise  the  arm  may  be  broken  off.  Do  not  use 
any  intermediate  tube  since  water  will  collect  in  it  and  stay  there. 
The  ordinary  rubber  stopper  is  about  25  mm.  long  and  tapers 
considerably.  Since  a  snug  fit  is  necessary  and  since  precautions 
must  be  taken  in  order  that  the  rubber  stopper  can  easily  and 
quickly  be  removed  from  the  absorption  bottle  at  the  end  of 
the  combustion,  cut  off  the  ends  of  the  stopper  in  such  a  way 
that  it  will  be  about  12-13  mm.  long  and  that  it  will  fit  in  the 
tube  without  leaving  any  spaces  for  the  collection  of  water 
between  the  stopper  and  the  tube.  A  longer  stopper  is  very 
difficult  to  remove  from  the  absorption  bottle  after  the  arm  has 
been  heated  by  the  hot  gases.  Red  rubber  stoppers  are  the  best. 
They  should  be  thoroughly  cleaned  and  all  moisture  removed. 
Sodium  hydroxide  will  help  to  remove  any  sulfur. 

The  gases  can  be  passed  through  either  the  inner  or  outei 
chamber  firs^-by  changing  the  position  of  the  large  stopper. 
Since  some  heat  is  evolved  in  the  absorption  of  the  water,  it  is 
better  to  pass  the  gas  through  the  outer  chamber  first.  In 
subsequent  combustions  the  gas  must  be  passed  in  the  same 
manner,  otherwise  there  is  the  possibility  of  the  gas  leaving  the 
bottle  with  some  moisture  which  it  has  taken  up  from  the  part 
already  more  or  less  saturated  in  a  previous  run. 

This  absorption  bottle  and  the  one  described  next,  when 
not  in  use,  should  be  kept  in  a  box  packed  with  cotton  for  proper 
protection  from  breakage  and  dirt. 

1  Carefully  breathe  through  the  stopper  for  a  moment  and  then  it  will  slip  over 
the  tube  more  readily.  Do  not  allow  any  excess  of  moisture  to  remain. 


ORGANIC  COMBUSTIONS  243 

Before  emptying  the  bottle,  remove  the  grease  from  the 
ground  surfaces  with  cotton. 

b.  The  Second  Absorption  Bottle.  The  carbon  dioxide  ab- 
sorption bottle  is  filled  with  moist  soda  lime  in  the  outer  chamber 
and  with  alumina-pumice  in  the  inner  chamber.  The  alumina 
must  be  used  since  the  gas  becomes  moiast  fter  passing  through 
the  soda  lime,  and  it  must  of  course  leave  the  bottle  in  as  dry  a 
condition  as  that  in  which  it  entered.  The  absorption  bottle  for 
this  work  is  constructed  with  the  idea  of  preventing  the  alumina 
from  absorbing  moisture  from  the  soda  lime  when  it  is  not  in  use. 
The  only  time  that  the  two  chambers  are  in  communication  is 
when  the  stopper  is  in  "  running  "  position. 

Place  some  cotton  in  the  outer  chamber  at  the  bottom  of  the 
bottle  around  the  holes  at  the  base  of  the  tube,  insert  a  plug  of 
cotton  or  a  cork  in  the  top  of  the  inner  standing  tube,  and  fill 
the  outer  chamber  with  three  layers  of  moist  soda  lime.1  The 
bottom  layer  and  the  top  layer  should  consist  of  soda  lime  with 
2  per  cent  of  water  and  of  2o-mesh  size,  the  middle  layer  of 
soda  lime  with  15  per  cent  of  water  and  of  i2-mesh  size.  Cover 
the  top  with  cotton  to  keep  it  in  place.  Then  quickly  fill  the 
inner  stopper  and  its  extension  tube  with  the  alumina-pumice, 
and  properly  protect  it  with  cotton,  as  in  the  case  of  the  first 
absorption  bottle  (p.  240,  see  footnote  5).  Be  sure  that  the 
flat  wad  of  cotton  covers  the  hole  in  the  stopper  and  that  most 
of  the  stopper  is  filled  with  the  drying  agent.  This  can  con- 
veniently be  done  if  it  is  filled  while  the  stopper  is  inclined 

1  Soda  lime  is  a  mixture  of  sodium  hydroxide  and  calcium  hydroxide,  and 
comes  on  the  market  in  granular  form  of  different  bizes  as  anhydrous  material 
and  with  different  amounts  of  moisture.  The  anhydrous  soda  lime  does  not 
give  rapid  and  complete  absorption.  (Compare  Lamb,  Wilson  and  Chancy,  "  Gas 
Masks  Absorbents,"  Journ.  Ind.  and  Eng.  Chem.,  11  (1919),  437-8.)  A  simple 
method  of  distinguishing  between  the  anhydrous  material  and  that  containing 
moisture  is  to  heat  the  sample  in  a  test-tube  and  note  whether  moisture  condenses 
on  the  upper  walls.  The  absorption  bottle  described  above  will  hold  a  total  weight 
of  about  20  grams  of  the  moist  soda  lime. 

"  Soda  asbestos,"  a  mixture  of  sodium  hydroxide  and  asbestos  in  granular 
form,  is  recommended  by  G.  L.  Kelly,  Journ.  Ind.  and  Eng.  Chem.,  8  (1916), 
1038.  See,  also,  Stetser  and  Norton,  Iron  Age,  102  (1918),  443-5;  and  Rogers, 
Canadian  Chem.  Journ.,  3  (1919),  122. 


244          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

with  the  hole  underneath.  Rapidly  clean  the  ground  surfaces, 
and  grease  and  put  together  as  described  above.  See  that  the 
cotton  does  not  get  on  the  greased  ground  surfaces  and  also  that 
the  arms  are  free  from  particles.  The  glass  stopper  for  one  arm 
is,  of  course,  not  necessary  in  this  bottle. 

Connect  this  absorption  bottle  with  the  first  absorption 
bottle  by  means  of  3.5  to  4  cm.  of  heavy- walled  rubber  pressure 
tubing.1  Here  also  do  not  grasp  the  bottle  itself,  but  take 
hold  only  of  the  arm  (compare  p.  242).  In  order  to  avoid  loss 
of  gas  the  arms  of  the  two  bottles  should  almost  meet,  but  care  is 
necessary  to  prevent  the  edge  of  one  from  rubbing  against  the 
other  since  the  glass  is  easily  chipped  off  when  they  are  brought 
together  inside  the  heavy  tubing.  Sometimes  it  is  advisable 
to  wire  these  joints  with  No.  16  copper  wire. 

The  gas  must  be  passed  into  the  outer  chamber  first. 

One  charge  of  soda  lime  (about  20  grams)  is  good  for  two 
combustions.  Sometimes  it  can  be  used  for  one  or  two  more, 
but  then  there  is  always  a  risk  that  the  absorption  may  not  be 
complete.  Soda  lime,  when  moist,  absorbs  carbon  dioxide  very 
rapidly  and  gives  off  considerable  heat.  Sometimes  the  soda 
lime  is  of  a  light  yellowish-brown  color  which  is  due  to  the 
presence  of  some  compound  of  iron  from  the  pots  in  which  it  is 
prepared.  As  the  absorption  progresses,  the  color  changes  to 
white  and  thus  it  gives  a  measure  of  how  much  soda  lime  is 
being  used.  It  is  noticed  that  the  color  changes  evenly  as  the 
absorption  takes  place.  The  presence  of  iron  also  helps  by 
accelerating  the  rate  of  absorption,  according  to  Guareschi.2 

On  account  of  the  heat  generated  during  the  absorption, 
droplets  of  water  will  sometimes  collect  on  the  walls  in  the 
upper  part  of  the  outer  chamber.  This,  of  course,  will  do  no 
harm. 

In  cases  where  many  combustions  are  being  run,  and  especially 
where  extreme  accuracy  is  required,  it  is  desirable  to  add  another 

1  Carefully  breathe  through  the  tubing.  Compare  note  on  the  rubber  stopper, 
p.  242. 

2  "  Supp.  ann.  all'enciclopedid,  di  chimica,"  Aug.,  1915,  Chem.  Abstracts,  10 
(1916),  25. 


ORGANIC  COMBUSTIONS  245 

absorption  bottle  filled  like  the  one  described  above  with  both 
soda  lime  and  alumina-asbestos.  This  is  weighed  also  and  its 
weight  indicates  when  the  first  bottle  will  no  longer  absorb 
carbon  dioxide  completely.  Or  instead,  the  second  bottle  of 
the  train  may  be  filled  only  with  soda  lime  and  the  third  one 
only  with  the  alumina-asbestos.  When  the  blank  run  (p.  246) 
is  made  with  this  latter  combination,  the  third  bottle  should  gain 
as  much  as  the  second  bottle  loses.  In  both  of  these  combina- 
tions the  sum  of  the  gains  of  each  bottle  at  the  end  of  a  com- 
bustion represents  the  total  increase  in  weight  due  to  carbon 
dioxide. 

Note  on  emptying  the  bottle. — The  soda  lime  becomes  hard 
and  caked  on  standing  after  the  absorption  of  carbon  dioxide 
and  care  must  be  exercised  in  removing  it.  A  pine  splinter  1 
is  useful  in  breaking  up  the  mass.  Often  it  becomes  necessary 
to  moisten  the  mass  to  soften  it.  Too  much  water  must  not 
be  used  and  it  must  be  poured  off  at  once,  otherwise  the  bottle 
may  be  cracked  on  account  of  the  heat  and  expansion  of  the  mass. 
Dilute  hydrochloric  acid  will  remove  the  particles  adhering  to  the 
walls.  The  alumina-pumice  must  also  be  renewed. 

c.  Guard  Tube  and  Palladious  Chloride  Solution. — To  the  car- 
bon dioxide  absorption  bottle  attach  an  ordinary  calcium  chloride 
tube  which  has  the  small  end  bent  at  90°,  and  which  has  been 
half  filled  with  the  alumina-pumice  mixture  kept  in  place  with 
plugs  of  cotton.  At  the  wide  end  of  the  tube  arrange  a  short 
glass  tube,  with  a  narrow  opening,  for  leading  the  gas  into  a  very 
dilute  solution  of  palladious  chloride.  By  leaving  the  drying 
tube  half  empty,  we  have  a  reservoir  for  any  of  the  palladious 
chloride  solution  that  might  be  drawn  back,  and  thus  it  is  pre- 
vented from  entering  the  absorption  bottle. 

The  palladious  chloride  solution  is  used  for  detecting  any 
carbon  monoxide  from  an  incomplete  combustion  and  also  for 
indicating  the  rate  of  absorption  of  the  products  of  combustion 
by  comparing  the  bubbling  here  with  that  in  the  bubble  counter. 
This  will  be  discussed  later  (see  p.  255).  The  solution  is  of  a 
light-yellow  color,  and  is  prepared  by  mixing  i  cc.  of  a 
1  See  foot-note,  p.  240. 


246          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

5  per  cent  solution  of  palladious  chloride  with  200  cc.  of  dis- 
tilled water.  From  this  very  dilute  solution  carbon  monoxide 
precipitates  metallic  palladium,  which  appears  as  black  colloidal 
particles.  The  solution  should  be  protected  from  any  carbon 
monoxide  in  the  room,  especially  when  the  laboratory  is  sup- 
plied with  water  gas.  When  in  use  the  bottle  should  have  a 
stopper  through  which  passes  the  glass  tube  and  which  has  a 
channel  cut  in  the  side  to  allow  the  gases  to  escape. 

The  short  glass  tube  mentioned  above  leading  into  the  pal- 
ladious chloride  solution,  should  be  drawn  out  into  a  narrow 
opening  like  the  one  in  the  bubble  counter,  in  order  that  the 
comparison  of  the  rate  can  be  made.  Since  the  viscosity  of  the 
sulphuric  acid  is  different  from  that  of  the  palladious  chloride 
solution  and  since  the  gas  pressures  are  also  different  in  each 
case,  the  rate 'of  bubble  formation  will  not  be  exactly  the  same, 
but  a  good  idea  of  the  "  normal  "  rates  can  be  obtained  by 
comparing  the  bubbling  before  the  substance  begins  to  burn. 

Instead  of  the  small  bottle  for  the  palladious  chloride  solution 
a  bubble  counter  can  be  used.  In  this  case  the  drying  tube  pre- 
ceding it  is  placed  in  a  horizontal  position.  It  is  difficult  to 
clean  the  bubble  counter.  If  metallic  palladium  is  precipitated 
it  can  be  dissolved  in  nitric  acid. 


V.  Method  of  Running  Blank  Determinations 

Since  there  is  the  possibility  of  many  errors  in  the  apparatus 
and  chemicals;  no  combustion  should  be  run  until  the  operator 
is  certain  that  everything  is  all  right.  The  only  satisfactory 
method  of  finding  this  out  is  to  run  a  blank  determination. 

After  the  apparatus  is  all  set  up  (without  the  boat  and  the 
absorption  train),  heat  the  combustion  tube  to  the  same  tem- 
perature that  will  be  used  later  in  the  determination,  that 
is,  to  a  cherry  red,  and  pass  in  purified  oxygen  gas  at  the  proper 
rate  during  the  course  of  about  two  hours.  This  procedure 
is  sometimes  called  "  glowing  out."  At  first,  moisture  will 
condense  near  the  open  end  of  the  tube.  After  this  moisture 
has  disappeared  attach  an  ordinary  calcium  chloride  drying  tube 


ORGANIC  COMBUSTIONS  247 

filled  with  granular  anhydrous  calcium  chloride,  which  is  properly 
protected  at  each  end  with  plugs  of  cotton.  Later  a  drying  tube 
filled  with  the  alumina-pumice  can  advantageously  be  used. 
The  combustion  tube  should  now  be  in  good  condition  but  the 
final  proof  is  made  as  follows: 

Remove  the  drying  tube  from  the  end  of  the  combustion 
tube,  and,  jwithout  changing  the  heating  or  the  oxygen  gas,1 
attach  the  ^ntire_absorrjtion  train  as  if  for  a  regular  combustion. 
The  bottles  can  be  supported  by  means  of  copper  wire  hooks 
hung  from  a  rod,  or  simply  allowed  to  stand  on  a  platform 
arranged  at  the  proper  height.  They  can  be  protected  from  the 
heat  of  the  furnace  by  means  of  an  asbestos  shield.  After 
thirty_or_iorty  minutes,  disconnect  the  absorption  train,  replace 
the  drying  tube,  and  immediately  weigh  the  absorption  bottles. 
See  p.  248  for  weighing  these  bottles.  Then  re-attach  the  ab- 
sorption train  and  allow  it  to  remain  under  the  same^conditions 
as  befonTfor  another  thirty  or  forty  minutes.2  Weigh  again  in 
the  same  order  as  before.  If  the  difference  in  each  case  is  not 
greater  than  0.0002  to  0.0003  gram  the  entire  apparatus  may  be 
considered  as  all  ready  for  the  combustion.  If  necessary  try 
another  blank  run.  If  the  first  absorption  bottle  continues  to 
gain,  then  the  purifying  train  is  probably  not  doing  its  work 
anoTlthe  alumina  should  be  renewed.  If  the  second  absorption 
bottkTcontaining  the  soda  lime  loses  weight  then  the  alumina- 
pumice  has  become  saturated  with  moisture  and  must  be  re- 
newed, or  it  is  insufficient  in  amount. 

Be  sure  to  attach  the  drying  tube  to  the  end  of  the  com- 
bustion tube,  every  time  the  absorption  train  is  removed. 

The  error  as  shown  by  the  blank  determination  should  be  a 
minimum,  not  more  than  the  error  in  weighing.  Other  errors  due 
to  burning  the  sample,  to  improper  weighing,  etc.,  are  likely  to 
occur,  but  these  can  be  more  readily  remedied  provided  the  ap- 
paratus itself  is  all  right. 

1  Do  not  allow  the  absorption  bottles  to  remain  long  stoppered  up  after  attach- 
ing since  the  pressure  of  the  oxygen  will  become  so  great  that  the  stoppers  will 
be  blown  out.     The  stoppers  can  be  put  in  "  running  "  position  just  before  attach- 
ment and  then  there  will  be  no  chance  for  trouble. 

2  During  this  time  the  substance  can  be  weighed  out.     See  p.  250. 


248          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

In  a  later  chapter  the  relative  weight  of  the  small  variations 
in  the  blank  runs  are  discussed  (p.  259). 

VI.  Weighing  the  Absorption  Bottles 

It  has  often  been  found  that  the  greatest  of  all  the  errors 
lies  in  the  weighing  of  the  absorption  bottles.  The  method 
given  here  is  not  claimed  to  be  perfect  but  in  our  experience  it 
gives  excellent  results.  When  it  is  considered  how  many  changes 
the  absorption  bottle  goes  through,  changes  due  to  the  passage  of 
hot  gases,  handling  in  making  the  connections,  deposits  from  the 
laboratory  atmosphere  of  dirt  and  moisture,  etc.,  it  is  no  wonder 
that  concordant  results  cannot  be  obtained  unless  great  care  and 
consistent  treatment  is  given. 

In  the  first  place,  the  absorption  bottles  should  be  weighed 
each  time  right  after  being  removed  from  the  combustion  tube.1 
Then  general  conditions  will  always  be  as  nearly  the  same  as 
practicable.  The  only  alternative  would  be  to  let  the  bottles 
stand  for  many  hours,  but  this  of  course  cannot  usually  be  done. 

The  bottles  must  be  scrupulously  clean  when  being  weighed, 
otherwise  surface  conditions  would  vary  too  much.  Wipe  them 
very  carefully  with  a  clean  dry  cloth  which  is  free  from  sizing 
and  starch.  A  towel  or  handkerchief  which  has  been  washed 
many  times  is  suitable.  Good  quality  lens  cloth  is  excellent  for 
this  purpose.  It  should  only  be  used  a  few  times.  Make  sure 
that  all  excess  of  grease  around  the  stopper  is  removed  by  the 
first  wiping  in  order  that  later  cleanings  will  not  change  the  weight 
on  this  account.  Wipe  very  thoroughly  every  part  of  the  bottle.2 
Be  careful  not  to  break  off  the  side  arms.  It  may  be  necessary 
to  rub  hard  at  first,  but  afterwards  this  should  not  be  done  since 
rubbing  with  a  dry  cloth  induces  a  static  charge  of  electricity 
and  this  apparently  has  much  to  do  with  discordant  results 
when  the  apparatus  is  weighed  under  these  conditions.3 

1  Dudley  and  Pease,  Journ.  Amer.  Chem.  Soc.,  15  (1893),  541;   Levene  and 
Bieber,  Journ.  Amer.  Chem.  Soc.,  40  (1918),  462. 

2  A  disadvantage  of  many  kinds  of  absorption  apparatus  is  that  they  cannot  be 
cleaned  properly. 

3  H.  K.  Miller,  in  an  article  on  "  Electrical  Disturbance  in  Weighing"   (Journ. 

.  Chem.  Soc.,  20  (1898),  428),  states  that  "  Careful  experiments  led  to  the 


ORGANIC  COMBUSTIONS  210 

A  change  of  several  milligrams  is  a  common  occurrence.  In 
order  to  dissipate  this  static  charge  some  analysts  allow  the 
absorption  apparatus  to  remain  for  a  definite  time  (four  minutes, 
for  example,  on  the  balance  pan  after  wiping  before  taking 
the  final  weight1)-  However,  there  is  a  question  whether 
the  conditions  are  always  the  same  since  the  wiping  is  not  always 
the  same.  The  bottle  cannot  be  left  too  long  before  weighing, 
because  as  the  charge  is  slowly  being  dissipated,  and  the  apparent 
weight  becoming  less,  it  will  begin  to  gain  on  account  of  the 
deposit  of  moisture,  and  no  constant  weight  will  be  found.2 

Another  method  to  obtain  a  constant  weight  after  the  wiping 
is  to  pass  the  thumb  and  one  finger  down  opposite  sides  of  the 
bottle  at  the  same  time,  and  then  immediately  set  the  bottle  on 
the  balance  pan  and  weigh.  Repeat  the  alternate  wiping  and 
passage  of  the  thumb  and  finger  and  weighing  until  the  weight 
is  constant  or  does  not  vary  in  two  consecutive  weighings  by  more 
than  0.0002  gram.  This  may  require  from  four  to  ten  complete 
repetitions.  Perhaps  the  use  of  the  fingers  on  the  bottle  just 
before  weighing  is  open  to  question,  but  the  method  gives  such 
good  concordant  results  and  is  so  rapid  that  we  are  willing  to 
recommend  it.  The  fingers  should  be  clean,  and  are  usually 

conclusion  that  in  wiping  the  flask  it  became  electrified,  and  that  this  static  charge, 
acting  on  the  floor  of  the  balance,  induced  on  it  a  charge  of  opposite  character, 
and  that  the  mutual  attraction  between  these  two  charges  of  electricity  had  the 
effect  of  apparently  increasing  the  weight  of  the  flask.  The  potential  of  the 
charge  would  vary  with  the  atmospheric  conditions  and  with  the  manner  of  wiping 
the  flask.  By  using  a  linen  cloth  in  very  dry  weather,  it  was  found  possible 
to  produce  a  charge  on  a  100  cc.  flask  which  would  require  0.08  gram  additional 
weight  to  restore  equilibrium.  A  high  charge  like  this,  however,  would  be  rapidly 
dissipated  and  the  flask  would  appear  to  lose  weight.  It  was  found  that  a  charge 
which  apparently  caused  an  increase  in  weight  of  about  o.oi  gram  would  be  re- 
tained quite  a  long  time,  and  one  might  readily  overlook  the  error  which  would 
thus  be  introduced.  It  was  further  found  that  a  small  charge  would  be  retained 
many  days  on  a  flask  kept  in  a  desiccator.  In  damp  weather  a  charge  would 
readily  pass  off  and  not  give  rise  to  an  error,  but  on  a  very  dry  day  the  practice  of 
wiping  glassware  just  before  weighing  is  liable  to  cause  serious  errors." 

1  L.  E.  Wise,  Journ.  Amer.  Chem.  Soc.,  39  (1917),  2062.     Small  apparatus  in 
connection  with  micro-analysis  was  used  in  this  work,  and  the  error  is  not  so  large. 

2  See  also  article  by  Rae  and  Reilly,  Chem   News,  114  (1916),  187-9,  200-3. 
Prof.  T.  W.  Richards  has  recommended  the  use  of  uranium  oxide  or  radium  l/o- 
mide  in  the  balance  case  to  dissipate  these  charges. 


250         LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

slightly  moist  while  handling  the  cloth  and  the  bottle,  and  the 
very  small  amount  of  moisture  and  grease  from  the  skin  that  may 
be  left  upon  the  surface  of  the  bottle  is  no  doubt  fairly  constant 
and  involves  an  error  far  less  than  that  caused  by  the  static 
charge.  The  bottle  should  not,  of  course,  be  touched  by 
the  fingers  except  as  directed. 

Difficulty  is  sometimes  experienced  in  obtaining  concordant 
results  on  damp  days,1  but  with  proper  precautions  good  results 
can  be  obtained  without  much  trouble. 

Since  the  absorption  bottles  are  often  shut  off  and  discon- 
nected under  different  pressures  of  oxygen,  it  is  well  to  release 
the  pressure  within  the  bottle  by  momentarily  opening  the  stop- 
cock, before  weighing. 

A  fine  analytical  balance  must  of  course  be  used,  and  it 
should  have  a  capacity  of  100  grams  for  accurate  work.  The 
absorption  bottles,  when  filled,  seldom  weigh  much  over  90  grams. 

For  an  excellent  discussion  of  and  careful  directions  for 
weighing,  calibration  of  weights,  etc.,  you  are  referred  to  an 
article  by  Rae  and  Reilly,  in  Client.  News,  114  (1916),  187-9, 
200-3,  and  to  the  forthcoming  book  on  quantitative  analysis 
by  Professors  H.  T.  Beans  and  Harold  A.  Fales  of  the  Depart- 
ment of  Chemistry,  Columbia  University. 

A  counterbalance  weight  or  bottle  is  sometimes  used  by  some 
analysts  in  weighing  the  absorption  apparatus.  A  similar 
piece  of  apparatus  is  made  to  weigh  approximately  the  same  by 
adding  lead  shot,  and  is  kept  beside  the  absorption  apparatus 
all  the  time  and  treated  just  the  same  in  every  way,  as  far 
as  possible. 

VII.  Weighing  the  Substance 

Since  organic  substances  are  generally  hygroscopic  and 
since  it  is  necessary  to  keep  all  moisture  away  from  the  sub- 
stance up  to  the  very  time  it  is  put  into  the  combustion  tube, 

1  Dudley  and  Pease,  Joitrn.  Amer.  Chem.  Soc.,  15  (1893),  540,  state,  "  If  we  may 
trust  our  experience  it  is  almost  impossible  to  make  satisfactory  combustions  in 
showery  weather."  These  authors  just  weighed  the  apparatus  direct  from  the 
furnace,  without  wiping.  Their  combustion  consisted  of  determining  carbon  in 
steel. 


ORGANIC  COMBUSTIONS 


251 


the  sample  should  be  weighed  in  a  closed  tube  and  kept 1  there 
until  transferred  to  the  combustion  tube.  This  is  done  in  the 
boat  tube  illustrated  in  Fig.  18.  On  account  of  its  shape  it 
is  known  in  laboratory  parlance  as  the  "  piggie  "  in  order  to 
distinguish  it  from  the  other  types  of  weighing  tubes.  The  legs 


^* 

! 

ui^; 


1 

1 


I 

O 

* 


are  placed  in  the  center  in  order  that  the  tube  will  rest  securely 
on  the  balance  pan.  If  they  are  near  the  stopper,  as  in  some 
models,  they  are  likely  to  slip  off  the  edge  of  the  ordinary  balance 
pan  and  then  the  tube  will  roll  and  the  boat  will  be  upset. 

1  If  the  substance  readily  sublimes,  it  should  be  weighed  out  just  before  beginning 
the  combustion  and  not  kept  in  the  boat  tube  for  any  length  of  time. 


252          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

The  porcelain  or  quartz  boat,1  properly  cleaned,  heated  in 
a  non-luminous  flame,  and  cooled  in  a  desiccator,  is  placed  in 
the  "  piggie  "  and  both  weighed  together.  Then  the  boat  is 
removed  with  tongs  or  forceps,  the  substance  added,  and  all 
weighed  together  again.  The  difference  in  weight  is  therefore 
the  weight  of  sample  used.  Similar  precautions  should  be  taken 
here  in  cleaning  the  outside  of  the  "  piggie  "  and  in  handling  it, 
as  given  for  the  absorption  bottles,  see  p.  248.  When  not  in  use 
both  the  boat  tube  and  the  boat  should  be  kept  in  the  desiccator. 

For  weighing  out  liquids,  see  p.  267. 

Ordinarily  the  amount  of  substance  used  for  a  combustion 
should  be  about  0.2  gram,  with  an  allowance  of  about  0.02  gram 
above  or  below,  since  the  actual  weight  need  not  be  exactly 
0.2  gram.  With  too  small  an  amount  of  substance  the  propor- 
tional errors  are  greater  and  with  a  larger  amount  too  much 
time  is  consumed  in  running  the  combustion.  The  weight  should 
be  carefully  taken  to  the  fourth  decimal  place,  and  properly 
recorded. 

The  substance  should  be  perfectly  dry.  If  necessary  spread 
it  upon  a  clean  dry  weighed  watch  glass,  determine  the  total 
weight  and  set  aside  in  a  desiccator  over  fresh  cone,  sulfuric 
acid  for  at  least  twenty-four  hours.  Then  weigh  again.  If  the 
weight  has  changed  put  the  substance  back  again  for  another 
period.  The  drying  can  be  hastened  by  first  placing  it  on  the 
watch  glass  as  above  and  setting  it  in  an  oven  heated  to  110°  C. 
and  after  several  hours  allowing  it  to  cool  in  a  desiccator.  This 
treatment  cannot  be  given  to  all  organic  substances  since  many 
sublime,  melt  or  decompose  at  that  temperature.  The  latter 
can  be  dried  in  a  vacuum  oven  at  about  50°,  or  in  a  vacuum 
apparatus  2  provided  with  a  drying  agent  and  kept  at  the  tem- 
perature of  boiling  acetone  (56°). 

In  case  it  should  be  necessary  to  determine  the  hydrogen 
in  a  substance  containing  moisture,  whose  moisture  content  is 

1  See  p.  236. 

2  Abderhalden's  "  Handbuch  der  Biochmischen  Arbeitsmethoden,"  I  (1910), 
296;  also,  in  Eimer  &  Amend,  N.  Y.,  catalogue,  under  the  name,  "  Vaccum 
Drying  Apparatus,  Abderhalden's," 


ORGANIC  COMBUSTIONS  253 

known,  the  hydrogen  cannot  be  directly  calculated  to  the  dry 
basis  like  the  carbon  since  the  hydrogen  has  been  obtained 
from  the  total  weight  of  water  absorbed  in  the  first  bottle. 
Therefore,  the  amount  of  water  in  the  sample  must  first  be 
subtracted  from  the  weight  of  water  absorbed,  and  the  hydrogen 
calculated  in  the  remaining  weight  of  water.  The  percentage 
can  then  be  obtained  using  the  weight  of  moisture-free  sample. 

VIII.  The  Combustion  Proper 

After  it  has  been  shown  by  the  blank  determination  (p.  246) 
that  the  entire  apparatus  is  all  right,  turn  off  the  heat  in  the  small 
section  (No.  i)  of  the  furnace  and  allow  this  end  of  the  tube 
near  the  purifying  train  to  cool  to  room  temperature.  Raise  the 
upper  half  to  hasten  the  cooling,  At  the  same  time  push  back 
the  two  other  heating  sections  in  order  that  the  space  for  the 
boat  will  become  cool. 

When  the  forward  end  is  cool,  turn  off  the  oxygen,  shut  off 
the  stop-cock  in  the  adjacent  drying  tube,  disconnect  the  purify- 
ing train  from  the  combustion  tube  and  pull  out  the  roll  of 
oxidized  copper  gauze  by  means  of  the  copper  wire  with  hook 
already  prepared  for  this  purpose,  making  sure  that  the  roll  is 
placed  upon  some  clean  surface  where  it  will  not  be  in  contact 
with  any  organic  material.  Then  carefully  remove  the  boat 
containing  the  weighed  amount  of  substance  from  the  boat  tube 
("  piggie  ")  by  means  of  forceps,  put  it  into  the  tube,  and 
shove  it  back  with  the  copper  wire  into  its  proper  position  about 
2.5  cm.  from  the  cerium  dioxide.  Replace  the  roll  of  oxidized 
gauze,  connect  the  purifying  train,  and  let  the  oxygen  pass 
through. 

Remove  the  guard  tube  from  the  other  end  of  the  combustion 
tube  and  attach  the  entire  absorption  train  (p.  247,  including  foot- 
note). If  the  substance  is  readily  distilled  out  of  the  boat  the 
absorption  train  should  be  attached  before  the  boat  is  put  into  the 
tube.  As  a  rule  this  is  not  necessary,  and  it  is  easier  to  attach 
the  absorption  train  afterwards. 

Regulate  the  passage  of  the  oxygen  in  such  a  manner  that  the 


254          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

bubbles  passing  through  the  sulfuric  acid  in  the  bubble-counter 
can  just  be  counted — that  is,  at  the  rate  of  about  three  to  four 
a  second. 

It  is  very  difficult  to  describe  in  detail  the  actual  method 
of  burning  an  organic  substance,  since  each  substance  has  its 
own  peculiarities  and  therefore  only  a  general  description  can  be 
given.  An  idea  as  to  how  the  substance  behaves  on  heating 
should  be  gained  beforehand,  if  sufficient  is  available,  by  gently 
heating  it  and  gradually  burning  it  in  a  boat  over  a  small  flame.1 
Gradually  move  the  large  heating  section  (No.  2)  a  centimeter 
at  a  time,  toward  the  boat,  until  most  of  the  cerium  dioxide- 
pumice  is  heated  to  redness.  At  the  same  time,  provided  the 
substance  is  not  too  volatile,  turn  on  the.  switch  and  allow  the 
small  heating  section  (No.  i)  to  become  warm  and  finally  hot, 
but  not  to  red  heat,  except  in  special  cases.  Also  heat  up  the 
last  section  (No.  3)  so  that  no  water  will  condense  in  that  end  of 
the  combustion  tube.  These  operations  ordinarily  require  about 
ten  minutes.  Then  move  the  large  heating  section  (No.  2) 
closer  to  the  boat  until  the  cerium  dioxide-pumice  is  all  being 
heated,  and  the  asbestos  plate  on  the  end  of  the  heating  section 
is  over  the  asbestos  plug  between  the  cerium  dioxide-pumice  and 
the  boat.  Now  very  slowly,  just  a  little  (0.5  cm.)  at  a  time,  move 
the  small  heating  section  (No.  i)  toward  and  finally  over  the  boat,  j 
With  substances  that  sublime  readily,  it  may  only  be  necessary 
to  bring  the  small  heating  section  (No.  i)  to  a  moderate  tem- 
perature to  drive  all  of  the  sample  over  the  cerium  dioxide- 
pumice.  With  an  active  catalyst  the  forward  points  of  the  im- 
pregnated pumice  will  glow.2  The  glow  cannot  always  be  seen; 
on  account  of  the  asbestos.  With  some  substances  the  forward 
part  of  the  pumice  mixture  will  appear  gray  as  the  decomposition 
begins.  This  is  probably  due  to  particles  of  carbon  which 
are  later  burned  completely.  The  burning  of  the  substance 
ordinarily  requires  from  ten  to  twenty-five  minutes,  depending 
upon  how  rapidly  the  substance  can  be  distilled  and  burned.  It 

1Weyl,  "Die  Methoden  der  organischen  Chemie,"  I  (1909),  17;  and  Wise, 
Journ.  Amer.  Chem.  Soc.,  39  (1917),  20. 

2  In  some  cases  the  little  roll  of  copper  oxide  gauze  in  front  of  the  asbestos 
appears  to  act  catalytically  since  it  also  glows  under  certain  conditions. 


ORGANIC  COMBUSTIONS  255 

is  well  to  take  the  longer  time  specified  for  burning  the  substance 
the  first  time  in  order  to  learn  any  of  its  peculiarities. 

During  the  course  of  the  combustion  the  operator  must  be  on 
the  alert  and  watch  not  only  the  burning  of  the  substance  but 
also  the  temperature  (compare  p.  231)  which  will  gradually  rise, 
I  and  the  rate  of  flow  of  the  oxygen  gas  coming  in  and  of  the  gases 
j  leaving  the  apparatus  through  the  palladious  chloride  solution. 
[Bubbles  of  gas  should  always  be  coming  through  the  palladious 
j  chloride  solution.     If  their  number  is  diminishing  so  rapidly 
!  that  it  appears  they  may  stop  then  more  oxygen  should  immedi- 
ately be  turned  on  in  order  that  there  may  be  an  adequate  supply 
for  complete  combustion.     The  presence  of  a  black  precipitate 
<  (colloidal  palladium)  in  the  palladious  chloride  solution  indicates 
that  carbon  monoxide  has  been  coming  through  the  absorption 
train,  and  therefore  that  the  combustion  is  incomplete  and  the 
determination  no  good  (p.  245). 

Soon  after  the  combustion  begins,  moisture  will  condense  in 

« the  forward  arm  of  the  alumina  bottle,  and  then  the  soda  lime 

j  bottle  will  become  warm.     The  general  operation  should  be  con- 

I  tinued    until    this   latter  absorption  bottle  is  practically  the 

same  as  the  first  one  in  temperature,  as  shown  by  the  hand. 

The  absorption  bottles  can  be  protected  from  the  heat  of  the 

furnace  which  is  not  very  great,  by  means  of  an  asbestos  shield. 

After  all  the  particles  of  carbon  have  disappeared  from  the 

boat  the  passage  of  the  oxygen  should  be  continued  for  at  least 

forty-five  minutes  in  order  that  all  the  products  of  combustion 

will  be  swept  out  and  properly  absorbed.     During  this  time  the 

temperature  may  gradually  be  reduced.     Little  care  is  needed 

!  after  all  the  substance  has  disappeared  and  the  boat  is  clean, 

I  except  to  see  that  the  gas  is  passing  all  right  and  the  tempera- 

rture  does  not  go  so  high  that  the  tube  is  melted.     Sometimes 

j:^particles_of_black  cupric  oxide  are  found  in  the  boat,  having 

been  swept  along  from  the  roll  of  oxidized  gauze  by  the  oxygen.1 

1  Levene  anofBieber,  Journ.  Amer.  Chem.  Soc.,  40  (1918),  461,  recommend  that 
a  small  coil  of  fine  platinum  gauze  be  placed  between  the  roll  of  oxidized  copper 
gauze  and  the  boat  to  prevent  the  particles  of  cupric  oxide  from  getting  into  the 
boat.  This  is  very  important  when  the  ash  of  the  substance  is  to  be  weighed  or 
analyzed. 


256          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

This  of  course  gives  the  appearance  of  unburned  carbon  and  its 
presence  is  annoying  since  the  end  of  the  combustion  is  indicated 
by  the  absence  of  black  carbon  particles.  That  the  particles 
do  consist  of  cupric  oxide  can  sometimes  be  established  by  the 
fact  that  they  do  not  disappear  after  prolonged  heating.  Later, 
when  the  boat  has  been  removed,  the  proof  can  be  made  definite 
by  seeing  if  they  are  soluble  in  nitric  acid.  It  should  be  noted 
however,  that  carbon  particles  formed  under  certain  conditions 
are  very  difficult  to  burn  (so-called  "  graphitic  "  carbon). 

If  moisture  collects  in  the  combustion  tube  just  in  front  of 
the  absorption  apparatus  and  persists  even  for  some  time  after 
the  substance  has  been  burned,  it  should  be  driven  through  by 
slowly  drawing  the  tube  further  into  the  furnace.  Consider- 
able care  is  necessary  for  this  gradual  heating  to  prevent  the  burn- 
ing of  the  rubber  stopper  and  also  the  cracking  of  the  tube.1 

After  the  tube  has  been  "  swept  out "  for  the  forty-five 
minutes  from  the  disappearance  of  the  last  particles  of  carbon 
in  or  around  the  boat,  the  absorption  bottles  are  closed,  dis- 
connected and  immediately  weighed  (p.  250).  The  guard  tube 
should  be  replaced  and  the  combustion  apparatus  is  then  ready  for 
another  determination  without  further  treatment. 

The  time  from  putting  the  boat  into  the  tube  until  the 
absorption  bottles  are  taken  to  the  balance  usually  is  from  an 
hour  and  ten  minutes  to  an  hour  and  a  half.  A  little  experi- 
ence soon  makes  it  possible  to  cut  this  down  to  an  hour,  or  to 
forty-five  minutes,  provided  no  special  difficulty  is  encountered 
in  burning  the  substance. 

Two  combustions  should  always  be  run  on  the  same  substance 
whenever  possible,  and  they  should  check  up  within  narrow 
limits.  See  discussion  of  results,  p.  258. 

NOTE 

If  no  cerium  dioxide  is  used  the  layer  of  cupric  oxide  wire  must 
be  much  longer,  40-70  cm.,  and  the  substance  must  be  burned  very 

1  If  a  gas  furnace  is  employed,  the  water  may  be  driven  over  by  holding  one  of  the 
hot  tiles  under  the  tube.  Some  operators  use  a  small  flame,  but  great  care  is 
necessary  to  prevent  cracking  the  tube  and  burning  the  stopper. 


ORGANIC  COMBUSTIONS  257 

slowly.  At  least  forty  minutes  is  required  just  for  the  burning  alone, 
and  some  substances  are  not  completely  oxidized  even  when  the  time 
is  considerably  extended. 

IX.  Calculations,  and  Discussion  of  Results 

Since  the  ratio  of  Eb  to  EkO  is  — ^ — -,1  which  is  equal  to 

18.016 

0.1119,  the  weight  of  hydrogen  in  the  weight  of  water  found  can 
ibe  calculated  by  multiplying  the  weight  of  water  by  0.1119. 
;  The  percentage  of  hydrogen  is  equal  to  the  weight  of  hydrogen 
j  multiplied  by  100  and  divided  by  the  weight  of  the  substance 

used.    Or  the  following  formula  may  be  used: 

H_  Weight  H2OX  2.016X100 
Weight  substance  X  18.01 6' 

For  logarithmic  calculation : 


Add 


Log.  wt.  H2O     = 
Log.  100  = 

Log.  0.1119        =9.0487—10 


Subtract    Log.  wt.  subs.      = 
Log.  per  cent  H  = 

Similarly,  since  the  ratio  of  C  to  C02  is  H  or  A,  which  is 
equal  to  0.2727,  the  weight  of  carbon  in  the  weight  of  carbon 
dioxide  found  can  be  calculated  by  multiplying  the  weight  of  the 
carbon  dioxide  by  TT  or  0.2727.  The  percentage  of  carbon 
is  equal  to  the  weight  of  the  carbon  multiplied  by  100  and  divided 
by  the  weight  of  the  substance  used.  Or, 

.  ~    Weight  CO2  X  3  X 100 
Per  cent  C  = ...  .  .     — r-      —77— 
Weight  substance  X 1 1 

1  Using  H  =  i.oo8. 


258          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 
For  logarithmic  calculation: 


Add 


Log.  wt.  CO2 
Log.  100 


Log.  0.2727        =9.4357-10 

Subtract     Log.  wt.  subs.    = 

Log.  per  cent  C  = 

For  ease  in  calculation,  a  table  of  four-place  logarithms  is 
given  on  pages  308-11. 

The  figures  showing  the  percentage  of  carbon  and  hydrogen 
should  not  be  extended  beyond  the  second  decimal  place.  The 
figures  beyond  the  second  decimal  place  in  this  work  are  not 
significant. 

Limit  of  Error. — In  order  to  be  able  to  compare  the  results 
of  analyses  to  see  whether  they  are  what  they  should  be,  some 
standard  is  necessary  for  the  limit  of  error.  The  criterion  for 
the  limit  of  error  in  good  analytical  work  is  one  part  in  one 
thousand.  Many  examples  can  be  given  to  show  that  the  deter- 
mination of  carbon  approaches  this  limit,  although  the  hydrogen 
is  not  so  good.  The  number  of  parts  per  thousand  error,  X, 
can  be  calculated  by  using  the  following  ratio:  Difference  of 
percentages  :  percentage  ::  X  :  1000;  or 

.__Diff.  of  per  cents  Xiooot 
per  cent 

where  one  percentage,  often  the  theoretical,  is  taken  for  the 
of  comparison.     This  is  made  more  clear  by  means  of  the  exam- 
ples which  follow : 

A  sample  of  cane  sugar  (C^IfeOn)  was  analyzed  with  the 
following  results:  0  =  42.05%;  H  =  6.48%.1  The  theoretical 
percentages  for  this  substance  are  0=42.09%;  H  =  6.46%.  The 

1  This  analysis  was  made  by  Mr.  R.  T.  Feliciano.  His  check  analysis  was 
C  =  42.i4%  and  42.15%;  H  =  6.46%  and  7.00%.  Similar  results  were  obtained  on 
the  same  substance  by  Mr.  H.  R.  Pyne:  C  =  42. 19%  and  42.07%;  H  =  6.23% 
and  6.26%.  Alumina-asbestos  mixture  was  used  in  the  first  instance,  and 
alumina-pumice  in  the  second. 


ORGANIC  COMBUSTIONS  259 

difference    between    the    theoretical  value  for  C  and  the  value 
actually  obtained  is  0.04.     Therefore  the  error,  expressed  as  parts 

,    .    0.04X1000     .  .  ,  , 

per  thousand,  is  -  -  which  equals  0.95    (approximately 

one  part  per  thousand).     Correspondingly,  for  H,  the  differ- 
ence between  the  theoretical  value  and  the  value  actually  found 

,  0.02X1000 

is  0.02;  and  --  -  —  -  —  =3.1  parts  per    thousand.     This  is  an 
6.40 

excellent  analysis.    The  same  comparison  can  of  course  be  made, 
and  should  be  made,  between  any  two  percentages  found. 

An  example  with  a  -very  high  percentage  of  carbon  :  Analysis 
of  anthracene  (CuHio):  Found,  0  =  94.17%;  H  =  5.7i%;1 
the  theory  being  0  =  94.34%;  H  =  5.66%.  The  error  for  C  is 

(94.34-94.i7)Xiooo  =  ^  thousand;  for  H,  the  error  is 

94-34 
(5.71  -5-66) 


The  "  allowed  "  error  for  carbon  ought  not  to  be  more  than 
2.5  parts  per  thousand,  and  never  over  5  parts  per  thousand. 
For  hydrogen,  the  "  allowed  "  error  ought  not  to  be  more  than 
20  parts  per  thousand,  and  never  over  30  parts  per  thousand. 

Now  it  is  possible  to  tell  the  extent  of  the  errors  which  are 
found  in  connection  with  the  blank  runs  (p.  247).  If  an  increase 
of  o.ooio  gram  is  noted  in  the  case  of  the  first  absorption  bottle, 
this  means  that  in  a  regular  combustion,  which  would  ordinarily 
require  about  twice  the  time  of  the  blank  run,  the  increase 
would  probably  be  about  0.0020  gram.  On  the  basis  of  using 
a  0.2  gram  sample,  this  gain,  counted  as  water,  would  be  equal 
to  o.i  i%  H  ;  and  if  the  substance  contained  5.0%  H,  the  error  due 
to  this  cause  alone  would  be  22  parts  per  thousand,  which  is 

1  This  analysis  was  made  by  Mr.  Henry  L.  Faust  and  is  the  first  one  which 
showed  us  that  alumina  could  be  used  in  organic  combustions.  The  same  substance 
was  later  analyzed  by  Mr.  David  I.  Hitchcock  with  the  following  results: 
C  =  94-36%  per  cent  and  94-12%;  H  =  5.57%  and  5.53%. 

For  the  sake  of  comparison,  the  very  first  results  obtained  by  using  the  alumina- 
pumice  mixture  are  added:  Salicylic  acid;  found,  C  =  60.77%  and  60.82%; 
H  =  4.47%  and  4.38%;  theory,  C  =  60.84%;  H=4.38%.  This  work  was  done 
by  Mr.  Geo.  H.  Walden. 


260          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

about  the  "  allowed  "  error.  Correspondingly,  if  the  same  gain 
of  o.oo  10  gram  is  noted  in  the  case  of  the  second  ^absorption 
bottle,  meaning  about  0.0020  gram  for  a  combustion,  on  the 
basis  again  of  a  0.2  gram  sample,  this  would  be  equivalent  to 
0.27%  C,  and  supposing  the  C  =  6o%,  the  error  on  this  account 
alone  would  be  4.5  parts  per  thousand,  which  is  /beyond  the 
ordinary  "  allowed  "  limit  of  error.  Any  other  error  in  the 
work  would  in  each  case  put  the  determination  way  beyond 
what  it  should  be. 

The  limit  of  error  of  0.0002  gram  in  weighing  alone  would, 
under  the  conditions  mentioned  above,  be  equal  to  4.4  parts  per 
thousand  for  the  hydrogen  and  0.9  parts  per  thousand  for  the 


These  figures  are  given  in  order  to  show  that  the  greatest 
care  at  all  times  must  be  exercised  in  carrying  out  the  work. 

Two  combustions  should  always  be  run  whenever  possible, 
and  they  should  check  up  within  the  limit  of  error  specified  above. 

NOTES 

1.  For  calculating  the  hydrogen  in  a  sample  which  contains  some 
moisture  and  whose  moisture  content  is  known,  see  p.  252. 

2.  The  percentage  of  C  and  H  in  a  hydrocarbon  should  add  up  to 
100=1=0.3  per  cent. 

3.  The  percentage  of  oxygen  in  a  compound  is  found  by  differ- 
ence.    This  method  of  calculating  throws  all  the  error  upon  the 
figure  for   this   element.     (For   a  method   of   determining   oxygen 
directly,  see  Boswell,   Journ.  Amer.  Chem.  Soc.,  35  (1913),  284-90; 
36  (1914),  127-32.) 

4.  The  empirical  formula  of  a  compound  is  found  by  dividing 
the  percentage  of  each  element  by  the  atomic  weight  of  the  element, 
and  the  ratio  is  then  expressed  in  whole  numbers  by  dividing  each 
term  by  the  lowest  value  or  by  some  simple  fraction  of  this  value. 
Since  these  numbers  as  found  by  analysis  seldom  are  whole  numbers, 
the  formula  which  has  been  found  in  this  way  should  always  be 
checked   up   by   calculating   the   percentage   composition   of   each 
element  from  the  formula  so  obtained  and  comparing  the  values  with 
those  found  experimentally.    They  should  agree  within  the  limit 
of  error  set  forth  above. 


ORGANIC  COMBUSTIONS  261 

The  molecular  formula  can  only  be  obtained  after  a  molecular 
weight  determination  has  been  made. 

Sometimes  the  empirical  formula  cannot  be  selected  since  the 
results  are  too  close  to  several  possibilities.  In  this  case  some 
derivative  of  the  substance  should  be  made  and  then  an  analysis 
carried  out  on  this  new  product.  Usually  the  figures  so  obtained 
will  settle  the  question.  (An  interesting  case  is  the  determination 
of  the  formula  of  cholesterol,  see  Glikin,  "  Chemie  der  Fette,  Lipoide 
und  Wachsarten,"  I  (1912),  334-5,  where  Reinitzer's  work  is  quoted 
from  Monatshefte,  9  (1888),  421.) 

X,  Some  Common  Errors  and  How  to  Avoid  Them 

Many  of  the  errors  have  already  been  discussed  in  connection 
with  different  parts  of  the  apparatus,  the  method  of  running 
the  combustion,  etc.,  and  many  errors  are  perfectly  obvious. 
Yet  it  has  been  our  experience  that  direct  attention  must  often 
be  drawn  to  some  errors  before  they  are  corrected,  and  it  is 
the  most  obvious  error  which  is  sometimes  committed.  There- 
fore all  that  have  been  noticed  in  actual  work  are  mentioned. 

Read  over  once  again  Liebig's  advice  which  is  quoted  at  the 
end  of  the  historical  introduction  (p.  223). 

The  Apparatus 

1.  Do  not  use  too  much  sulfuric  acid  in  the  bubble  counter. 

It  may  suck  back  or  be  splashed  over  and  cause  trouble 
with  the  rubber  tubing  and  stopper  (p.  227). 

2.  The  pre-heater  should  not  be  heated  to  such  an  extent  that 

the  glass  tube  melts.     Watch  the  temperature  (p.  231). 

3.  Use  heavy-walled  "  pressure  "  rubber  tubing.     Other  kinds 

are  not  gas  tight  and  do  not  fit  snugly.  Wire  joints,  if 
necessary,  with  No.  16  copper  wire,  and  use  a  pair  of 
pliers  to  tighten  them  (p.  244). 

4.  See  that  the  glass  stoppers  are  properly  greased  (p.  229). 

Attach  a  piece  of  twine  to  prevent  them  from  being  blown 
out  in  case  of  excess  of  pressure  (p.  229,  (footnote)). 

5.  Use  red  rubber  stoppers,  and  clean  them  well,  inside  as  well 

as  out  (p.  242). 


262          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

6.  Cut  the  rubber  stopper  properly  for  connecting  the  first 

absorption  bottle  to  the  combustion  tube  (p.  242). 

7.  Do  not  use  a  piece  of  glass  or  rubber  tubing  to  connect  the 

first  absorption  bottle  with  the  combustion  tube  (p.  242). 

8.  Do  not  fill  the  stoppers  of  the  absorption  bottles  with  cotton. 

The   space   is  needed  for  the  drying  agent,  especially  in 
the  soda  lime  bottle  (p.  243). 

9.  Do  not  allow  the  two  absorption  bottles   to  come  so  close 

that  the  ends  of  the  arms  are  chipped  (p.  244). 
10.  See  that  there  is  space  provided  above  the  palladious  chloride 
solution  for  any  emergency  in  case  of  back  pressure  (p.  245.) 

The  Chemicals 

1.  Purify  ail  oxygen  by  passing  it  through   the  pre-heater 

(p.  228). 

2.  Use  the  specified  soda  lime  for  both  drying  and  absorption 

trains  (pp.  229,  243).     See  that  it  is  of  proper  size  and 
moisture  content. 

3.  Use  the  same  drying  agent  in  the  drying  train  that  is  used 

in  the  absorption  train  (p.  230). 

4.  Do  not  expect  the  materials  in  the  drying  train  to  last  for- 

ever. 

5.  Keep  the  stop-cocks  of  the  U-tubes  in  the  drying  train 

closed  when  not  in  use  (p.  229). 

6.  See  that  the  copper  spirals  are  properly  made  and  fit  all  right 

(P-  235)- 

7.  Do  not  use  cupric  oxide  wire  for  carbon  and  hydrogen  that 

has  been  used  for  determining  nitrogen,  unless  it  has  been 
re-treated  (p.  236). 

8.  Do  not  use  alumina  that  has  been  heated  too  long  or  too 

high  (p.  238). 

9.  Keep    the    palladious    chloride    solution    stoppered    except 

when  in  use  (p.  246). 

Weighing 

T.  Use  a  proper  analytical  balance  and,  if  you  use  a  rider,  see 
that  it  is  the  right  one  for  your  balance. 


ORGANIC  COMBUSTIONS  263 

2.  The  absorption  bottles  should  not  have  anything  on  them 

when  weighed.     Detach  rubber  stopper  and  tubing. 

3.  Wipe  each  absorption  bottle  carefully  and  do  not  record  the 

weight  until  you  are  satisfied  that  it  is  all  right  and  that 
you  can  duplicate  it  (p.  249). 

4.  Weigh  the  bottles  in  the  same  order  each  time  and  try  to 

take  approximately  the  same  time  in  weighing.  A 
slightly  different  weight  is  found  when  the  bottle  has  been 
standing  and  is  cold. 

5.  Wipe  off  all  grease  from  around  the  stopper  of  the  bottle 

before  you  begin  to  weigh.  After  that  be  careful  not  to 
wipe  off  any  more  in  all  other  weighings  (p.  248). 

6.  Make  proper  record  of  all  weighings  in  a  neat  manner  so 

that  all  figures  are  known.  Do  not  leave  anything  to 
guess  work.  Do  not  throw  away  any  papers  until  the 
work  is  completed  and  accepted. 

Blank  Runs 

1.  Continued  findings  of  gain  in  weight  of  first  absorption  bottle 

shows  that  drying  train  needs  attention,  or  that  rubber 
stoppers  are  burning. 

2.  Loss  in  weight  of  first  absorption  bottle  usually  means  that  (i) 

grease  has  been  wiped  off  the  stopper,  (2)  particles  of  the 
drying  agent  have  been  blown  out  of  the  bottle,  or  (3)  the 
drying  agent  is  "  spent  "  and  moisture  is  being  removed 
from  it  by  the  dry  gas  from  the  drying  train. 

3.  Loss  in  weight  of  either  bottle  may  be  due  to  chipping  the 

glass  at  the  end  of  the  arms  (p.  244). 

4.  Loss  in  weight  of  the  soda  lime  bottle  is  usually  due  to 

"  spent  "  drying  agent,  or  not  enough  of  the  good  material. 
Fill  up  the  stopper  (p.  243).  Sometimes  it  is  necessary  to 
add  a  third  bottle  (p.  244). 

5.  Loss  in  weight  may  be  due  to  the  fact  that  the  gas  is  being 

passed  through  the  bottle  in  the  wrong  direction,  (p.  242). 

6.  Loss  in  weight  may  be  due  to  loss  of  particles  from  side  arms. 

See  that  these  are  scrupulously  clean  (p.  242). 

7.  Gain  in  soda  lime  bottle  is  generally  due  to  the  burning  of 


264          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

rubber  stoppers  in  the  pre-heater  or  forward  end  of  the 
combustion  tube.  If  the  rubber  stopper  next  to  the  dry- 
ing train  in  the  pre-heater  tube  is  burned,  some  of  the  gases 
may  go  through  the  drying  train  incompletely  absorbed, 
and  then  they  will  be  burned  in  the  combustion  tube. 
The  rubber  stopper  should  not  become  spongy. 

The  Combustion 

Some  of  the  troubles  mentioned  under  the  previous  heading 
apply  here  also. 

1.  Do  not  fail  to  prove  your  apparatus  by  running  a  blank 

determination. 

2.  Keep  enough  oxygen  in  the  apparatus  to  supply  the  needs 

all  the  time.  See  that  it  is  always  bubbling  through  the 
palladious  chloride  solution  (p.  255). 

3.  Do  not  try  to  burn  the  substance  too  fast  before  you  are  fully 

acquainted  with  the  apparatus. 

4.  Remember  that  the  combustion  needs  attention  all  the  time. 

Do  not  try  to  do  too  many  other  things  at  the  same  time. 
Too  much  effort  will  be  lost. 

5.  Black  particles  in  the  boat  near  end  of  the  combustion  may  be 

carbon  or  cupric  oxide  (p.  255). 

6.  Do  not  let  the  small  section  become  too  hot,  especially  at 

the  beginning  (p.  254). 

7.  If  you  weigh  the   absorption  bottle  with  the  little  stopper 

for  one  arm,  do  not  fail  to  keep  it  safe  and  weigh  it  again 
with  the  bottle  later. 

8.  It  is  most  desirable  as  a  rule  to  run  a  blank  determination 

between  two  consecutive  combustions,  since  all  the  moisture 
and  carbon  dioxide  may  not  have  been  removed,  especially 
if  the  time  after  the  substance  has  been  burned  is  cut 
short. 

9.  If  the  percentage  of  hydrogen  in  a  determination  is  high  and 

the  carbon  low,  this  may  be  due  to  the  fact  that  the  gases 
have  not  been  completely  driven  through  the  first  bottle. 
Attach  the  absorption  train  to  the  drying  train,  pass  the 
oxygen  through  for  twenty  minutes  and  weigh  again. 


ORGANIC  COMBUSTIONS  265 

XI.  Combustion   of   Substances   Containing   Nitrogen,   Sulfur, 
Halogens,  Phosphorus,  Sodium,  etc. 

Nitrogen. — With  an  active  catalyst  and  plenty  of  oxygen, 
the  nitrogen  is  oxidized  to  nitrogen  dioxide.  This  is  true  even 
with  substances  containing  nitrogen  in  the  so-called  "  unoxi- 
dized  "  form,  as  in  amines,  amides,  etc.  Nitrogen  dioxide  is 
absorbed  more  or  less  by  the  drying  agent  and  completely 
absorbed  by  soda  lime.  Therefore  it  is  necessary  to  keep  it 
from  going  into  the  absorption  train.  Lead  peroxide  (PbC^)1, 
kept  at  3Oo°-32o°,  is  the  best  means  of  "  fixing  "  the  nitrogen 
dioxide  and  preventing  it  from  leaving  the  combustion  tube. 
The  temperature  must  be  tried  out  ahead  of  time  to  find  out 
the  working  conditions.  Too  high  a  temperature  (above 
350°)  will  cause  the  decomposition  of  the  lead  nitrate  which  is 
formed,  -  and  also  will  convert  the  PbO2  into  Pb^04.  Since 
water  vapor  acts  upon  lead  nitrate  giving  a  basic  nitrate  and 
liberating  nitric  acid  which  is  not  all  reabsorbed  by  the  lead 
peroxide,  it  is  necessary  to  mix  an  equal  amount  of  Pb304 
(minium)  with  the  lead  peroxide.  Some  PbsCU  for  use  can 
readily  be  obtained  by  heating  some  of  the  lead  peroxide  in  a 
tube  or  open  dish  to  4oo°-45o°. 

The  lead  peroxide  mixture  (7-8  grams)  is  placed  in  a  tube  of 
hard  glass,  Fig.  19,  which  fits  the  combustion  tube  snugly,  and 
put  in  position  F  as  shown  on  the  general  diagram,  p.  233  (see 
also  p.  236).  Or  it  is  placed  in  a  large  boat,  14  cm.  long,  pref- 
erably with  the  end  open  (broken  off)  toward  the  catalyst.2 

Lead  peroxide  is  very  hygroscopic  and  care  must  be  used  in 
handling  it  and  proving  it  in  the  blank  run.  It  must  be  very 
pure,  free  from  any  organic  particles  such  as  dust,  fibers  from 

1Lead  peroxide  was  used  by  Liebig  and  contemporary  workers  in  organic 
combustions  to  absorb  acidic  gases,  and  in  1876  by  Kopfer,  when  he  introduced  the 
catalytic  method  (p.  219),  but  Dennstedt  has  done  the  best  work  on  how  to  use 
it.  See  his  "  Anleitung  zur  vereinfachten  Elementaranalyse,"  3  Aufl.  (1910), 
66-70,  90. 

*Levene  and  Bieber,  Journ.  Amer.  Chem.  Soc.,  40  (1918),  460,  recommend 
putting  the  lead  peroxide  directly  into  the  tube  with  alternate  layers  of  a  mixture 
of  it  with  asbestos, 


266          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

filter  paper,  etc.  It  must  also  be  free  from  lead  oxide  since 
this  absorbs  carbon  dioxide  at  a  high  temperature.1 

The  combustion  must  be  run  slower  than  when  the  substance 
contains  no  nitrogen.2 

Cupric  oxide  also  absorbs  nitrogen  dioxide.  The  copper 
nitrate  formed  is  only  slowly  decomposed  around  300°,  and  if  the 
latter  part  of  the  cupric  oxide  just  preceding  the  lead  peroxide 
mixture  is  not  well  heated  between  combustions,  the  nitrate 
may  accumulate  to  such  an  extent  that  it  will  entirely  block 
the  combustion  tube.3 

--  4/ioLES 


/4cm.- 


TUBE.  FOR  LEAD  PEROXIDEMIXTURE 

FIG.  19. 

NOTES 

1.  For  the  electrolytic  preparation  of  the  lead  peroxide  you  are 
referred  to  Dennstedt's  book  mentioned  above,  p.  265;   and  to  King- 
scott  and  Knight,  "  Methods  of  Quantitative  Organic  Analysis  " 

(iQH),  35- 

2.  For  other  methods  of  combusting  organic  substances  contain- 
ing  nitrogen,    see    Gattermann,    "  Practical    Methods   of   Organic 
Chemistry,"  3d  Amer.  Ed.,  (1914),  and  especially,  F.  G.  Benedict, 
"  Elementary  Organic  Analysis  "  (1900),  59-64. 

3.  For  estimating  carbon,  hydrogen,  and  nitrogen  simultaneously, 
see  Dennstedt  and  Hassler,  Ber.,  41  (1908),  2778. 

Sulfur. — For  determining  carbon  and  hydrogen  by  the  cataly- 
tic method  when  the  substance  contains  sulfur,  the  same  pro- 
cedure is  used  as  above  when  nitrogen  is  present.  The  sulfur 
is  fixed  as  lead  sulfate. 

1  Lassar-Cohn,  "  Arbeitsmethoden,"  Allgemeine  Theil,  4  Aufl.  (1906),  286. 

2  Reimer,  "  On  Rapid  Organic  Combustions,"  Journ.  Amer.  Chem.  Soc.,  37 
(1915),  1636-8. 

3  Fisher  and  Wright,  Journ,  Amer.  Chem.  Soc.,  40  (1918),  868, 


ORGANIC  COMBUSTIONS  267 

Other  methods,  when  a  catalyst  is  not  used,  are  discussed 
in  the  books  mentioned  in  the  foreword. 

Halogens. — The  lead  peroxide  mixture  also  serves  for  fixing 
chlorine  and  bromine,  but  not  iodine.  A  roll  of  silver  gauze 
or  a  long  boat  containing  so-called  "  molecular  silver,"  prepared 
by  treating  silver  halide  residues  with  granular  zinc,  is  used  for 
all  the  halogens. 

Phosphorus,  Sodium,  Mercury,  etc. — Only  notes  and  refer- 
ences will  be  given  for  these. 

Phosphorus  is  often  converted  into  phosphoric  acid  which, 
on  account  of  its  physical  state,  holds  back  particles  of  carbon. 
It  is  then  necessary  to  use  an  alundum  boat,  which  is  removed 
after  most  of  the  carbon  has  been  burned,  dialyzed  to  get  rid  of 
the  phosphoric  acid,  dried,  and  put  back  with  the  carbon  in  it 
for  complete  conbustion. 

Sodium  and  other  basic  elements  retain  carbon  in  the  ash 
as  carbonate.  F.  G.  Benedict,  "  Elementary  Organic  Analysis" 
(1900),  70,  recommends  the  admixture  of  lead  chroma te  and 
potassium  dichromate  with  the  substance  to  expel  the  carbon 
dioxide.  Or  the  ash  can  be  analyzed  by  the  ordinary  methods. 
See  also  Kuzirian,  "  The  estimation  of  CO2  in  the  ash  of  plant 
and  animal  substances,"  Journ.  Ind.  and  Eng.  Chem.,  8  (1916), 
89,  who  uses  sodium  paratungstate. 

Mercury. — "  The  simultaneous  determination  of  carbon, 
hydrogen,  and  mercury,"  V.  Grignard  and  A.  Abelman,  Bull, 
soc.  Mm.,  19  (1916),  25-7. 

XII.    Combustion  of  Liquids,  Gases,  and  Explosive  Substances 

Liquids. — If  the  liquid  substance  has  a  boiling-point  above 
about  170°,  it  may  generally  be  weighed  directly  in  the  boat 
as  if  it  were  a  solid.  There  should  be  no  delay,  of  course,  after 
weighing — the  boat  should  be  put  directly  into  the  combustion 
tube. 

Lower  boiling  liquids  are  weighed  in  a  sealed  bulb  with  a 
capillary  tube.1  This  tube  is  then  carefully  broken  off  at  a 

1  Liebig,  "  Instructions  for  the  Chemical  Analysis  of  Organic  Bodies."    Trans 
by  Gregory  (1839),  20. 


268          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

file  mark,  and  the  bulb  and  the  piece  are  put  into  the  boat 
in  such  a  way  that  the  tube  will  rest  on  the  end  of  the  boat 
near  the  cerium  dioxide,  and  immediately  placed  in  the 
combustion  tube.  It  is  slowly  distilled  out  and  burned  in  the 
usual  manner.  Part'cles  of  glass  in  the  bulb  aid  in  the  dis- 
tillation (suggested  by  M;.  E.  M.  Slocum).  The  substance 
should  not,  of  course,  be  allowed  to  be  carbonized  within  the 
bulb. 

A  smal'  thin- walled  glass  bulb,1  3-5  mm.  in  diameter,  such 
as  is  often  employed  for  molecular  weight  determinations 
by  the  vapor  density  method,  is  used.  It  is  filled  by  placing 
it  with  the  open  capillary  tube  dipping  into  the  liquid  to  be 
analyzed,  contained  in  a  dish,  inside  a  vacuum  desiccator.  The 
suction  is  then  turned  on  and  after  a  few  minutes  air  is  allowed 
to  re-enter  the  desiccator.  This  causes  the  liquid  to  be  drawn 
into  the  bulb.  The  bulb  should  be  weighed  before,  and  again 
after  sealing. 

Very  low-boiling  liquids  must  be  driven  into  the  combustion 
tube  somewhat  as  in  the  case  when  a  gas  is  analyzed.  They 
often  form  explosive  mixtures. 

REFERENCES 

Benedict,  loc.  cit.,  73-9;  Clarke,  "Note  on  the  combustion  of 
volatile  organic  liquids."  Jour.  Amer.  Chem.  Soc.,  34  (1912),  746-7. 

Gases.  Since  gases  form  explosive  mixtures  with  oxygen, 
the  oxygen  must  always  be  in  very  great  excess  when  the  gas  is 
slowly  being  driven  into  the  combustion  tube.  The  gas  is  held 
in  a  gas  burette  in  which  it  is  measured,  and  slowly  sent  through 
a  capillary  tube  into  the  combustion  tube.  A  long  cupric  oxide 
spiral  near  the  entrance  helps  to  cause  thorough  mixing  and  to 
prevent  "  back  firing." 

1  This  small  bulb  can  be  made  as  follows:  Heat  and  draw  out  a  piece  of  ordinary 
glacs  tubing,  and  cut  off  one  end  of  the  narrow  tube  at  the  shoulder.  Then  soften 
in  the  flame  the  end  which  has  been  cut  off,  and,  with  the  other  end  as  a  mouth- 
piece, blow  a  bulb.  It  is  completed  by  cutting  the  narrow  tube  at  the  desired 
length. 


ORGANIC  COMBUSTIONS  269 

Explosive  Substances.  These  are  weighed  out  as  usual  in  a 
boat  and  then  mixed  with  three  or  four  volumes  of  cupric  oxide 
(which  is  free  from  moisture,  etc.)  or  quartz  sand. 


DIVISION  B 

THE  DETERMINATION  OF  NITROGEN 

I.  Historical  Introduction1 

Gay-Lussac  and  Thenard  (1810)  were  the  first  to  determine 
nitrogen  in  organic  substances.  Their  method  consisted  in  burn- 
ing the  substance  in  the  presence  of  potassium  chlorate  and 
analyzing  the  gases  evolved  (compare  carbon  and  hydrogen, 
p.  218).  Later  (1815)  cupric  oxide  was  introduced  by  them 
and  is  still  used  up  to  the  present  time.  Liebig  used  this 
same  method,  improving  it  so  that  he  could  collect  and  weigh 
the  water  and  carbon  dioxide,  and  measure  the  nitrogen  as  a 
gas.  Dumas  2  burned  the  substance  in  an  atmosphere  of  carbon 
dioxide,  prepared  from  lead  carbonate  in  the  end  of  the  closed 
tube,  and  collected  the  nitrogen  in  a  eudiometer  over  mercury 
and  a  solution  of  potassium  hydroxide  to  absorb  the  carbon 
dioxide.  He  also  used  reduced  copper  to  reduce  any  oxides  of 
nitrogen  which  may  be  formed.  Thus  he  laid  the  complete 
foundation  of  the  method  which  is  the  most  general  and,  when 
properly  carried  out,  as  accurate  for  nitrogen  as  any  yet  devised. 

Erdmann  and  Marchand  3  used  an  outside  generator  for  the 
carbon  dioxide,  and  Hugo  Schiff4  devised  the  azOtometer 
which  has  been  such  a  great  help  in  handling  the  gases.  It  is 
of  considerable  interest  to  note  how  the  azotometer  was  developed 
and  modified.  The  references  for  the  different  forms  (and  each 
reference  contains  a  sketch  of  the  apparatus  for  which  the 
author  is  sponsor),  are  found  in  Dennstedt's  history,  p.  40,  and 

1  Dennstedt,  "  Die  Entwickelung  der  organischen  Elementaranalyse,"  Ahren's 
"Sammlung  chemischer  und  chemisch-technischer  Vortrage,"  IV  (1899),  29. 

2  Ann.  Chlm.  phys.,2  (1831),  198;  Dennstedt's  history,  p.  35. 
ZJ.  pr.  Chcm.,  14  (1838),  213. 

4  Zeitschr.  anal.  Chem.,  7  (1868),  430. 


270          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

Richter's  "  Organische  Chemie,"  n  AufL,  I  (1909),  7.  Mag- 
nesite  (magnesium  carbonate)  later  displaced  the  lead  and  other 
carbonates  and  is  most  generally  used  when  the  substance  is 
burned  in  a  closed  tube.1 

Many  organic  substances  when  heated,  expecially  in  the  pres- 
ence of  soda  lime,  give  up  their  nitrogen  as  ammonia,  or  some 
simple  amine.  This  method  was  used  for  the  determination  of 
nitrogen  by  Varrentrapp  and  Will2  in  1841.  The  ammonia 
formed  is  absorbed  in  a  known  amount  of  standard  acid  and  the 
excess  of  acid  titrated  back  with  alkali.  From  this,  the  amount 
of  acid  neutralized  by  the  ammonia  is  obtained  and  the  ammonia 
and  nitrogen  can  then  be  calculated.  This  method  is  not 
applicable  to  substances  in  which  the  nitrogen  is  in  such  com- 
bination as  in  the  nitro-group,  azo-group,  etc. 

Some  forty  years  later,  in  1883,  Kjeldahl 3  brought  forth  an- 
other method  which  on  account  of  its  ease  of  manipulation  and 
applicability  to  many  substances  which  are  analyzed  for  nitrogen 
in  great  numbers,  has  been  of  inestimable  service.  The  Kjeldahl 
method  consists  of  heating  the  substance  with  cone,  sulfuric 
acid  usually  in  the  presence  of  a  catalyst,  such  as  a  mercury  salt, 
potassium  permanganate  or  cupric  sulfate.  This  procedure 
converts  the  nitrogen  into  ammonium  sulfate.  The  mixture  is 
then  diluted,  made  strongly  alkaline  with  sodium  hydroxide, 
and  distilled.  The  solution  of  ammonia  which  constitutes  the 
distillate  is  collected  in  a  definite  amount  of  standard  acid  and 
the  analysis  completed  by  back  titration,  etc.,  as  outlined  in 
the  previous  paragraph.  Some  substances,  especially  those  with 
the  nitrogen  in  the  ring  are  not  completely  decomposed  by  the 
method.  Otherwise,  by  different  modifications  for  increasing 
the  temperature  by  adding  potassium  hydrogen  sulfate,  by 
reducing  nitro-compounds  just  previously,  etc.,  the  method 
has  found  wide  application. 

Within  very  recent  years  micro-methods  for  determining 

1  This  is  the  method  outlined  in  Gattermann,  "  Practical  Methods  of  Organic 
Chemistry,"  3d  Amer.  Ed.  (1914),  90. 

2  Ann.  Chem.  Pharm.,  39  (i84i),  257. 
3Zeitschr.  anal.  Chem.  22  (1883),  366. 


ORGANIC  COMBUSTIONS  271 

nitrogen  by  both  th.e  Dumas  and  Kjeldahl  methods  have  been 
devised  by  Pregl.1 

Since  the  Dumas  or  absolute  method  is  so  generally  appli- 
cable even  though  it  is  slow  and  must  be  carefully  watched, 
it  is  the  one  selected  and  described  in  the  following  pages.  The 
chief  difficulties  are  in  obtaining  pure  carbon  dioxide  and  in 
preparing  the  cupric  oxide  so  that  it  will  not  continue  to  give 
off  occluded  gases.  These  points  are  fully  discussed  later  and 
need  not  be  repeated  here.  The  modifications  used  bring  the 
results  within  a  fair  limit  of  error  (compare  p.  302).  One 
must  work  with  gases  and  with  pressures  above  and  below 
atmospheric.  On  this  account  many  stop-cocks  are  necessary 
to  make  the  apparatus  efficient.  However,  although  the  array 
of  stop-cocks  may  appear  formidable  at  first  you  will  rapidly 
become  familiar  with  their  uses  and  then  good  results  will  soon 
follow. 

II.  List  of  Apparatus  and  Chemicals  for  the  Determination  of 

Nitrogen 

Apparatus 

1.  *  Electric  combustion  furnace  (p.  283). 

2.  *  Pyrex  combustion  tube,  76  cm.  long  and  15  mm.  inside 

diameter,  for  72  cm.  combustion  furnace  (p.  283). 

3.  *  Asbestos  paper  for  lining  trough  of  the  furnace  (p.  231.) 

4.  *  Copper  gauze,  40  mesh,  i  square  foot  (pp.  283-4). 

5.  *  Copper  wire,  No.  16,  3  feet  long. 

6.  Two  red  rubber  stoppers,  one-holed,  size  i  or  o  depending 

upon  the  diameter  of  the  combustion  tube;  one  rubber 
stopper,  one-holed,  for  the  dropping-funnel;  one  rubber 
stopper,  three-holed,  for  the  generator  flask;  one  rubber 
stopper,  two-holed,  for  the  safety  bottle  connected  with 
the  generator;  and  one  rubber  stopper,  three-holed,  for 
the  Erlenmeyer  filtering  flask  in  connection  with  the  ma- 
nometer. 

1  Pregl,    Abderhalden's    "  Handbuch    der    biochemischen   Arbeitsmethoden," 
V  (1912),  1332.    See  also  Fisceman,  Rend,  accad.sci.  fis.  et  mat.  Napoli,  [3],  21 
135-42. 


272          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

7.  *  Rubber  pressure  tubing  (p.  283). 

8.  *  One  U-tube,  with  ground  glass  stoppers,  12.5  cm.  (5  inches) 

(p.  282). 

9.  Glass  beads  for  the  U-tube  (p.  282). 

10.  *  One  porcelain  or  quartz  boat  (pp.  284,  292). 

11.  *  One  special  weighing  tube,  boat  tube  ("  piggie  ")  (p.  251). 

12.  Azotometer,   50  cc.,  graduated  to  o.i    cc.,   and  reservoir 

(p.  285). 

13.  Carbon  dioxide  generator  (p.  275),  consisting  mainly  of: 

a.  Erlenmeyer  filtering  flask,  750  cc. 

b.  Dropping-funnel,  200  cc. 

c.  Stout  safety  bottle,  about  200  cc. 

d.  Bulbed  test-tube,  6  inches. 

e.  Capillary  tube. 

14.  Seven  stop-cocks. 

15.  Erlenmeyer  filtering  flask  (in  connection  with  manometer) 

(p.  282). 

1 6.  Manometer  stand  (p.  281). 

17.  One  length  of  glass  tubing  for  manometer,  about  140  cm. 

1 8.  Water  pump  or  oil  vacuum  pump  (p.  282). 

19.  Thermometer  (p.  298). 

20.  *  Crucible  tongs. 

21.  *  One  pair  of  pliers. 

22.  *  Desiccator. 

23.  Mercury,  45°-5°°  grams  (pp.  275,  281,  286)0 

24.  One  test-tube  of  Pyrex  glass,  for  the  reduced  copper  spiral 

(p-  285). 

25.  Glass  wool  or  asbestos  for  the  above  (p.  285). 

26.  *  Stop-cock  grease,  E.  &  A.  (p.  283). 

Chemicals 

1.  100  grams  of  cupric  oxide,  wire  form. 

2.  Pure  sodium  bicarbonate,  100  grams  for  each  determination. 

3.  Cone,  sulfuric  acid,  for  use  in  generator  and  U-tube. 

*  Those  pieces  of  apparatus  vhich  are  starred  (*)  are  the  same  as  on  the  list 
for  the  carbon  and  hydrogen  determination  and  given  on  pp.  223-4. 


ORGANIC  COMBUSTIONS  273 

4.  Potassium  hydroxide  (100  grams  dissolved  in  100  cc.  water 
makes  a  solution  which  is  good  for  two  determinations). 

III.  Topical  Outline  of  General  Method  of  Procedure 

1.  Set  up  the  electric  combustion  furnace  (p.  283). 

2.  Select  the  combustion  tube,  and  if  necessary  cut  to  proper 

length  and  "  round  "  the  edges  (p.  284). 

3.  Fill  the  combustion  tube  (p.  284). 

4.  Assemble  the  carbon  dioxide  generator  (p.  275),  the  manom- 

eter (p.  281),  and  accompanying  stop-cocks  and  U-tube 
(p.  282). 

5.  Clean,  attach  and  test  the  azotometer  (nitrometer),  (p.  285). 

6.  Prepare  the  carbonate  mixture  and  i  :  i  sulfuric  acid  for  the 

generator  (p.  277),  and  the  mercury  and  the  i  :  i  potas- 
sium hydroxide  solution  for  the  azotometer  (pp.  286-7). 

7.  Prepare  the  cupric  oxide  wire  in  the  combustion  tube  by 

heating  it  under  diminished  pressure  and  allowing  it  to 
cool  in  an  atmosphere  of  carbon  dioxide  (p.  288). 

8.  Test  the  entire  apparatus  (p.  293). 

9.  Prepare  the  reduced  copper  spiral  and  allow  it  to  cool; (p.  285). 

10.  Weigh  out  the  substance  (p.  292). 

11.  The  combustion  proper  (p.  294);  the  furnace  can  be  cold  or 

hot  at  the  beginning  (p.  294). 

a.  Insert  the  boat  containing  the  substance  (pp.  294-5). 

b.  Insert  the  reduced  copper  spiral  (pp.  294-5). 

c.  Connect  up  the  entire  apparatus,  evacuate,  and  flood 

with  carbon  dioxide  (p.  295). 

d.  Heat  the  reduced  copper  spiral  to  redness  for  about 

five  minutes  in  order  to  drive  out  occluded  gases 

(P-  295)- 

e.  Test  with  azotometer  full  of  the- potassium  hydroxide 

solution  to  see  if  all  non-absorbable  gases  have 
been  removed  from  the  apparatus,  or  reduced  to 
a  minimum  (pp.  295-6). 

/.  Heat  the  layer  of  cupric  oxide  wire  to  redness,  being 
careful  not  to  burn  the  substance  (p.  295),  and  at 
the  same  time 


274          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

g.  Reduce  the  flow  of  carbon  dioxide  to  such  an  extent 
that  it  will  just  keep  the  products  of  combustion 
moving  toward  the  azotometer,  using  the  stopper 
in  the  U-tube  for  regulating  the  gas  (p.  28-2), 
and  allowing  the  excess  of  carbon  dioxide  to  escape 
through  No.  2  (p.  276). 

h.  Slowly  heat  the  oxidized  copper  spiral,  and  then  com- 
bust the  substance  (p.  296). 

i.  Drive  over  all  the  remaining  nitrogen  gas  with  carbon 
dioxide  by  gradually  increasing  its  flow  (p.  297). 

j.  Close  stop-cock  No.  6  (between  the  azotometer  and 
the  combustion  tube),  wash  the  gas  in  the  azotom- 
eter with  one  portion  of  the  potassium  hydroxide 
solution,  while  the  reservoir  is  in  the  low  position 
(I),  and  then  wash  with  cold  distilled  water,  which 
has  been  recently  boiled  to  drive  out  dissolved  air, 
until  all  the  potassium  hydroxide  solution  is  out 
of  the  azotometer  and  the  reservoir  (p.  297). 

k.  Level  the  liquid  in  the  reservoir  and  the  azotometer, 
place  a  thermometer  in  the  water  in  the  top  of  the 
azotometer,  and  after  twenty  to  thirty  minutes 
record  the  volume  of  the  gas  by  reading  the  lower 
meniscus,  the  temperature,  and  the  corrected 
barometer  reading  (p.  298). 

/.   Calculate  the  percentage  of  nitrogen  (p.  300). 

12.  In  order  to  have  the  tube  ready  for  another  combustion, 
remove  the  reduced  copper  spiral,  draw  air  through  the 
tube  while  it  is  still  hot  in  order  to  oxidize  the  copper  that 
has  been  reduced  in  the  combustion,  then  flood  the  appa- 
ratus with  carbon  dioxide.  Now  it  may  be  used  again 
at  once,  or  it  can  be  closed  off  and  the  cupric  oxide  allowed 
to  cool  in  the  atmosphere  of  carbon  dioxide  (p.  299). 


ORGANIC  COMBUSTIONS  275 

IV.  The  Apparatus  and  How  to  Put  it  together,  with  Notes  on 

Manipulation 

i.  The  Carbon  Dioxide  Generator. — Since  the  substance  is 
burned  in  an  atmosphere  of  carbon  dioxide  and  since  the  nitrogen 
gas  itself  is  measured  directly,  the  carbon  dioxide  must  be  as  free 
as  possible  from  any  impurities  which  will  not  be  absorbed  by 
the  potassium  hydroxide  solution  in  the  azotometer.  The  car- 
bon dioxide  can  be  prepared  from  sodium  bicarbonate  1  or  from 
normal  potassium  carbonate.  On  account  of  the  expense  in- 
volved in  the  use  of  the  potassium  carbonate,  the  sodium  bicar- 
bonate is  generally  used  and  unless  otherwise  stated  is  always 
referred  to  in  the  following  discussion.  The  same  style  of 
generator  can  be  used  in  either  case. 

The  generator  must  be  one  that  can  be  used  with  pressures 
above  or  below  atmospheric.  Many  are  the  styles  of  generators 
that  have  been  used  and  published,  and  the  one  described  herein 
contains  no  new  features.  It  has  simply  been  selected  as  one 
that  can  easily  be  assembled  from  ordinary  apparatus.  At  the 
end  of  this  chapter  an  innovation  is  described  in  connection  with 
the  stop-cock  (see  p.  278). 

A  glance  at  the  general  diagram  of  apparatus,  Fig.  20, 
shows  that  an  Erlenmeyer  filter  flask  (about  750  cc.)  is  sur- 
mounted by  a  dropping-funnel  of  about  2oo-cc.  capacity.  In 
order  to  equalize  the  pressures  in  the  two  chambers  an  outside 
connection  is  made  from  the  top  of  the  dropping-funnel  through 
stop-cock  No.  ii  2  to  the  top  of  the  filter  flask.  A  three-holed 
rubber  stopper  is  used  in  the  filter  flask  and  the  third  hole  is  con- 
nected with  a  stout  empty  bottle  and  this  with  a  stop-cock  (No. 
2)  leading  into  a  bulbed  test-tube  containing  about  8  cc.  (108 

1  Sodium  bicarbonate  was  chosen  by  Bradley  and  Hale  (Journ.  Amer   Chem. 
Soc.,  30  (1908),  1090)  who  prepared  carbon  dioxide  which  was  of  extreme  purity 
containing  only  one  part  of  impurity  (that  is,  gas  not  absorbed  by  potassium  hydrox- 
ide solution)  in  30,000  to  40,000  parts  of  the  gas. 

2  Stop-cock  No.  ii  is  added  to  close  off  the  acid  and  prevent  it  from  absorbing 
CO2  from  the  lower  chamber  and  forming  a  partial  vacuum.     This  is  particularly 
true  in  the  case  of  potassium  carbonate  when  that  is  used.     It  is  also  added  in 
order  that  the  reservoir  of  the  dropping-funnel  may  be  recharged  without  allowing 
much  air  to  get  into  the  lower  part  of  the  generator. 


276 


LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 


grams)  of  mercury.  This  acts  as  a  safety  outlet  for  the  excess 
of  carbon  dioxide.  Generally  the  tube  from  the  stop-cock  should 
dip  about  3.5-4  cm.  into  the  mercury.  The  bulb  in  the  test- 


tube  prevents  the  mercury  from  splashing  out  of  the  tube.  The 
top  of  the  test-tube  should  be  loosely  packed  with  cotton  to 
prevent  fine  particles  of  mercury  from  being  thrown  out.  The 
empty  bottle  serves  as  a  safety  bottle  to  prevent  any  of  the 
mercury  from  being  drawn  into  the  generator  in  case  the  stop- 
cock is  not  closed  at  the  proper  time.  Whenever  carbon  dioxide 


ORGANIC  COMBUSTIONS  277 

is  being  passed  through  the  apparatus  under  its  own  pressure, 
stop-cock  No.  2  should  always  be  left  open  in  order  that  any 
excess  of  pressure  can  be  taken  care  of. 

A  capillary  tube,  i  mm.  inside  diameter,  bent  upwards  at  the 
lower  end,  is  attached  to  the  stem  of  the  dropping-funnel,1  and 
is  arranged  to  deliver  the  acid  beneath  the  surface  of  the  bicar- 
bonate mixture.  This  insures  a  more  even  generation  of  carbon 
dioxide  and  better  control  than  when  the  acid  is  allowed  to  drop 
from  the  stem.  The  upward  bend  prevents  the  carbon  dioxide 
from  going  up  the  stem  of  the  dropping-funnel.  Modifications 
will,  of  course,  suggest  themselves  to  each  operator  for  his  con- 
venience. 

One  hundred  grams  of  pure  sodium  bicarbonate  and  100  cc.  of 
recently  boiled-and  cooled  water  are  used  as  a  single  charge  for  the 
generator.  This  is  not  enough  water  to  dissolve  all  the  bicar- 
bonate, but  is  sufficient  for  the  purpose.  The  bicarbonate  mixture 
should  be  removed  and  fresh  material  put  in  after  each  combustion. 
Otherwise  the  supply  of  carbon  dioxide  may  fail  at  a  critical  time 
when  there  is  no  possibility  of  making  the  change.  One  hundred 
and  fifty  cc.  of  a  mixture  of  one  part  of  cone,  sulfuric  acid  and 
one  part  of  distilled  water  in  the  dropping-funnel  will  serve  for 
at  least  two  combustions. 

Sodium  bicarbonate  and  water  react  to  give  carbon  dioxide 
even  at  the  ordinary  temperature,  and  at  elevated  temperatures 
the  bicarbonate  is  rapidly  converted  into  the  normal  carbonate. 
Reduction  of  the  pressure  produces  the  same  reaction  at  lower 
temperatures,  as  will  be  noticed  during  the  operation. 

Potassium  carbonate  has  an  advantage  over  sodium  bicar- 
bonate as  a  source  of  CO2  in  that  it  can  be  used  in  a  fairly  con- 
centrated solution.  The  solution  of  the  carbonate  is  made  up 
with  a  specific  gravity  (1.45-1.5)  somewhat  greater  than  that 
of  the  sulfuric  acid  (1.4)  and  the  carbonate  solution  is  put  into 
the  dropping-funnel  instead  of  the  filter  flask  of  the  generator 
described  above.  The  carbonate  solution  of  sp.gr.  1.45-1.5 

1  The  joints  should  be  wired,  since  the  rubber  gradually  swells  and  becomes 
loose. 


278          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

contains  43-47  per  cent  of  potassium  carbonate  and  is  prepared 
by  dissolving  about  85-90  grams  of  dry  pure  normal  potassium 
carbonate  in  100  cc.  of  recently  boiled  water,  and  the  sulfuric 
acid  solution  is  prepared  by  mixing  100  cc.  of  cone,  sulfuric  acid 
and  100  cc.  of  water.  The  relative  specific  gravity  of  the 
carbonate  solution,  when  cold,  can  be  tested  if  a  hydrometer  is 
not  at  hand  by  seeing  if  a  drop  of  brombenzene  (1.496/16°) 
or  of  chloroform  (1.498/15°)  sinks  and  a  drop  of  ethyl  bromide 
(1.468/13°)  just  floats  in  it,  provided,  of  course,  the  influence  of 
surface  tension  is  guarded  against  by  stirring.  Since  the  car- 
bonate solution  dissolves  carbon  dioxide  with  the  formation 
of  the  bicarbonate  which  is  much  less  soluble  than  the  normal 
carbonate  and  crystallizes  out,  and  since  this  absorption  produces 
a  partial  vacuum,  the  surface  of  the  solution  should  be  covered 
with  a  thin  layer  of  petroleum  oil 1  to  prevent  access  of  the 
carbon  dioxide  to  the  liquid. 

A  generator  with  a  special  stop-cock  2  for  dropping  the  liquid 
arranged  for  equalizing  the  pressure  above  and  below  the  outlet 
in  the  stop-cock  is  shown  in  Fig.  21.  The  equalizing  is  done 
through  a  connection  made  by  means  of  the  annular  groove 
in  the  key  of  the  stop-cock.  No  matter  which  position  the 
key  occupies  there  is  always  communication  between  the  atmos- 
phere in  the  lower  flask  and  that  in  the  upper  flask.  One 
arm  of  the  stop-cock  is  extended  until  it  opens  above  the  liquid 
in  the  upper  container.  No  outside  connection  is  necessary. 
The  liquid  enters  at  an  aperture  in  the  lower  part  of  the  ex- 
tended arm  and  is  delivered  through  a  small  glass  tube  sealed  in 
at  this  opening.  Two  styles  of  stop-cocks  are  shown  "in  the 
diagram,  using  the  same  general  principle  in  each. 

If  the  flasks  are  used  as  shown  they  must  be  securely  fastened 
by  clamps  close  to  the  lips.  The  upper  flask  can  be  filled  through 

1  Compare  Watson  Smith,  Jr.,  "  Quantitative  determination  of  the  carbonyl 
group  in  Aldehydes,  Ketones,  etc."  Chem.  News,  93  (1906),  83;  where  paraffin  oil 
is  used  to  protect  Fehling's  solution  from  absorbing  carbon  dioxide.     Also  given 
in  H.  Meyer,  "  Analyse  und  Konstitutionsermittelung  organischer  Verbindungen," 
2.  Auflage,  p.  683. 

2  Fisher,  Journ.  Ind.  and  Eng.  Chem.,  10  (1918),  1014. 


ORGANIC  COMBUSTIONS 


279 


a  funnel  attached  by  means  of  a  piece  of  rubber  tubing.     The 
liquid  will  flow  down  the  inside  walls  and  not  drop  into  the  ex- 


Fig,  la 


•ig.2 


Fig.  1 

Reproduced,  with  permission,  from  the  Journal  of  Industrial  and  Engineering  Chemistry. 

FlG.  21. 

tended  tube.     The  arrangement  and  kind  of  flasks  can  be  changed 
as  desired. 


280         LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

FURTHER  NOTES  AND  REFERENCES 

F.  Blau  x  used  the  potassium  carbonate  and  sulfuric  acid  as  de- 
scribed above.  He  found  that  50-100  CG.  of  the  carbonate  solution 
was  needed  to  drive  the  air  out  of  the  apparatus  and  only  about  20  cc. 
was  needed  for  the  combustion  proper.  This  latter  amount  in  a 
blank  run  yielded  only  0.07-0.1  cc.  of  unabsorbed  gas  in  the  azotom- 
eter,  and  the  author's  experience  has  been  similar.  Blau  remarks 
that  it  is  not  necessary  to  boil  the  concentrated  carbonate  solution 
since  it  absorbs  a  much  smaller  amount  of  air  than  an  equal  volume  of 
water  and  only  a  small  volume  is  used.  He  adds  that  a  more  dilute 
solution  cannot  be  used  without  having  been  boiled,  since  it  absorbs 
a  large  amount  of  air  and  moreover  greater  amounts  of  the  solution 
must  be  used. 

Young  and  Caudwell2  used  potassium  carbonate  also  in  their 
generator.  They  found  that  "  the  carbon  dioxide  formed  in  this 
manner  does  not  contain  o.i  cc.  of  air  per  5  litres,"  which  means  an 
impurity  of  less  than  i  part  in  50,000  (compare  below  and  p.  275). 
Fieldner  and  Taylor  3  used  this  method,  and  state  that  "  there  was 
little  difficulty  in  clearing  the  cold  tube  of  air  so  that  the  CO2  was 
completely  absorbed,"  and  yet  in  reply  to  a  letter  from  the  author, 
Dr.  Fieldner  said  that  they  tried  three  samples  of  potassium  carbon- 
ate before  they  obtained  carbon  dioxide  that  gave  only  a  minimum 
of  tiny  bubbles  which  were  never  totally  absorbed. 

The  purest  carbon  dioxide  that  has  ever  been  obtained  and 
accurately  analyzed  and  recorded  was  prepared  by  Bradley  and  Hale  4 
in  connection  with  work  on  physical  constants  of  the  gas.  They 
used  sodium  bicarbonate  in  the  form  of  a  paste  and  cone,  sulfuric 
acid.  In  guarding  against  impurities  from  the  air  they  found  it 
even  necessary  to  place  mercury  jackets  around  all  rubber  connec- 
tions since  air  diffuses  in  as  well  as  carbon  dioxide  diffuses  out  through 
the  rubber.  In  their  article  other  recorded  attempts  to  prepare  pure 
C02  are  given  and  discussed.. 

Sodium  bicarbonate  in  the  form  of  dry  powder  has  been  used 
in  connection  with  nitrogen  determinations  in  the  open-tube  method. 

lMonatsheftefur  Chemie,  13  (1892),  277. 

2 "  Apparatus  for  the  Supply  of  Carbon  Dioxide  in  the  Determination  of 
Nitrogen  in  Organic  Compounds  by  the  Absolute  Method,"  Journ.  Soc.  Chem. 
Ind.,  26  (1907),  184. 

3  Journ.  Ind.  and  Eng.  Chem.,  7  (1915),  109. 

4  Journ.  Amer.  Chem.  Soc.,  30  (1908),  1090. 


ORGANIC  COMBUSTIONS  281 

It  is  heated  in  a  separate  tube.  Dennstedt l  selected  this  substance 
for  his  work.  Gattermann  2  also  describes  how  to  use  it.  However, 
it  is  difficult  to  handle  and  contains  occluded  air. 

Thudichum  and  Wanklyn  3  recommend  a  mixture  of  potassium 
bichromate  and  sodium  carbonate  for  yielding  carbon  dioxide  by 
direct  heating. 

Magnesite  (MgCOa)  is  used  as  the  source  of  CO2  in  the  closed- 
tube  method4  (see  p.  270),  but  it  usually  contains  small  amounts 
of  occluded  air. 

Carbon  dioxide  from  a  Kipp  generator  cannot  be  used  even  when 
the  marble  lumps  have  been  boiled  with  water  on  account  of  the 
occluded  air. 

The  tanks  of  liquid  CC>2  as  obtained  on  the  market  contain  con- 
siderable amounts  of  air  and  therefore  cannot  be  used. 

2.  The  Manometer,  Accompanying  Stop-cocks,  U-tube,  etc. — 

• — Since  diminished  pressures  are  used  in  the  nitrogen  determina- 
tion, it  is  necessary  to  have  a  manometer  in  connection  with 
the  apparatus  in  order  that  the  operator  will  be  able  to  under- 
stand what  to  do.  The  U-form  is  recommended  as  shown  in  the 
general  diagram  (p.  276).  It  is  made  of  ordinary  glass  tubing 
and  is  attached  to  a  wooden  stand  provided  for  this  purpose. 
The  long  arm  should  be  at  least  82  cm.  in  length  and  the  short  arm 
at  least  55  cm.  The  short  arm  is  surmounted  with  an  inverted 
small  test-tube  with  a  plug  of  cotton  at  the  bottom  to  prevent  dust 
particles  from  getting  into  the  tube  and  to  prevent  mercury  from 
splashing  out.  With  the  ordinary  glass  tubing  of  about  5  mm. 
bore,  approximately  250  grams  of  mercury  is  required.  The 
column  of  mercury  when  at  rest  should  extend  in  each  arm 
40-41  cm.  from  the  lower  bend.  If  it  is  much  higher  than  this, 
it  may  be  drawn  over  the  top  when  a  good  vacuum  is  being 
obtained.  A  meter  stick  may  be  attached  to  the  board  to 
measure  the  difference  in  heights  of  the  two  columns,5  if  the  actual 

1  Dennstedt,  "  Anleitung  zur  vereinfachten  Elementaranalyse,"  3  Auflage,  129. 

2  Gattermann,  "  Practical  Methods  of  Organic  Chemistry,"  trans,  by  Schober 
and  Babasinian,  3d  Amer.  Ed.  (1914),  p.  101. 

3  Journ.  Chem.  Soc.,  22  (1869),  293. 

4  Gattermann,  loc  cit.,  p.  94. 

5  Or  short  paper  scales  can  be  used.     Select  any  point,  x,  not  less  than  38  cm. 
above  the  lowest  bend  in  the  glass  tubing,  and  attach  a  narrow  strip  of  paper  near 


282         LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

pressure  is  desired.  The  pressure  within  the  apparatus  may  be 
calculated  by  subtracting  this  difference  in  height  from  the 
barometer  reading  at  the  time. 

The  manometer  is  connected  with  an  Erlenmeyer  heavy- 
walled  filtering  flask  and  this  is  provided  with  an  outlet  stop- 
cock (No.  9)  and  another  stop-cock  (No.  10)  leading  to  a  suitable 
pump.  When  a  water  pump  is  used  the  connection  is  made 
to  go  to  the  bottom  of  the  filtering  flask  in  order  that  any  water 
which  may  come  over  on  account  of  unequal  pressure  in  the 
water  main  will  be  sucked  right  out  as  soon  as  the  greater  water 
pressure  returns.  A  good  water  pump  will  give  a  pressure  in  the 
apparatus  as  low  as  the  vapor  tension  of  the  water  at  its  par- 
ticular temperature.  In  winter  when  the  temperature  of  the 
water  may  be  8°,  at  which  the  vapor  tension  of  the  water  is  7.99 
mm.,  the  pressure  within  the  apparatus  may  approach  8  mm., 
but  in  summer  when  the  temperature  of  the  water  may  be  as 
high  as  23°  a  pressure  cannot  be  obtained  lower  than  21  mm., 
which  is  the  vapor  tension  of  the  water  at  that  temperature. 
A  good  oil  pump  can  be  substituted  for  the  water  pump  with 
much  advantage. 

The  outlet  of  the  Erlenmeyer  filtering  flask  is  connected  by 
means  of  a  stop-cock  (No.  8)  to  a  T-tube  which  joins  the  genera- 
tor and  a  U-tube  with  ground  stoppers.  The  U-tube  is  filled 
with  glass  beads  and  just  enough  cone,  sulfuric  acid  is  added  to 
make  a  seal  at  the  bottom  and  no  more.  The  glass  beads  serve 
to  prevent  the  acid  from  being  splashed  upon  the  stop-cocks. 
The  acid  attacks  the  grease  and  causes  leakage  as  well  as  sticking 
of  the  stoppers.  The  acid  is  used  to  prevent  an  excess  of  moisture 
from  the  carbon  dioxide  from  getting  into  the  combustion  tube 
and  it  also  shows  which  way  the  gases  are  flowing.  The  amount 

the  top  and  one  near  the  bottom  of  the  stand.  Measuring  from  the  point  x,  mark 
on  the  papers  numbers  showing  28  to  38  cm.  up  and  down,  respectively.  The 
numbers  may  vary  according  to  the  positions  of  the  papers.  Ruled  centimeter 
paper  is  very  convenient,  and  when  this  is  used  it  should  not  be  attached  until 
a  definite  point  opposite  a  centimeter  line  has  been  located.  In  order  to  calculate 
the  pressure  within  the  apparatus,  add  the  numbers  on  the  lower  and  upper  scales 
opposite  the  top  of  the  mercury  meniscus  and  subtract  the  sum  of  these  numbers 
from  the  barometer  reading  at  the  time. 


ORGANIC  COMBUSTIONS  283 

of  carbon  dioxide  flowing  into  the  combustion  tube  is  regulated 
by  one  of  the  stoppers  (No.  5). 

All  connections  are  made  with  short  lengths  of  heavy-walled 
rubber  "  pressure  "  tubing. 

All  stop-cocks  should  be  carefully  cleaned  and  greased  with 
a  good  stop-cock  grease,  such  as  that  prepared  by  Eimer  & 
Amend,  New  York  (see  p.  229).  Do  not  plug  up  the  opening  in 
the  key  with  grease.  Too  much  grease  is  worse  than  too  little. 
Also  do  not  use  vaseline,  since  it  has  no  "  body."  Great  care 
should  always  be  exercised  in  turning  the  keys  in  the  stop-cocks  to 
see  that  they  fit  tightly  and  do  not  leak.  Never  turn  the  key  by 
using  only  one  hand.  Support  the  other  side  of  the  stop-cock 
with  the  other  hand  and  use  just  a  little  pressure  when  turning 
the  key.  Fasten  the  keys  with  wire  or  twine,  not  with  elastic 
bands,  to  avoid  possible  breakage  (compare  p.  229).  The  parts 
of  all  stop-cocks  should  be  numbered  in  order  that  they  will  be 
properly  assembled. 

An  alternative  method  of  preparing  the  manometer  is  to  use 
a  straight  glass  tube,  about  85  cm.  long,  dipping  directly  into 
mercury.  The  bottle  containing  the  mercury  should  be  of  such 
a  size  that  when  the  excess  of  CO2  is  passing  out  of  the  tube  the 
pressure  will  be  all  right  for  the  conditions  involved,  that  is, 
the  layer  of  mercury  through  which  the  gas  must  pass  will  be 
somewhat  greater  than  that  in  the  azotometer.  Otherwise  the 
gas  would  pass  out  at  this  opening  instead  of  going  into  the 
azotometer.  The  method  has  the  advantage  of  less  apparatus, 
but  the  pressure  in  the  generator  cannot  so  easily  be  regulated 
as  in  the  method  described  above,  and  there  is  more  space  to  be 
emptied  of  air  and  kept  filled  with  C02  all  the  time-  the  combus- 
tion is  being  run,  since  stop-cock  No.  8  cannot  be  shut  off. 

3.  The  Electric  Combustion  Furnace. — An  electric  com- 
bustion furnace  of  the  multiple  unit  type  is  the  most  convenient 
furnace  to  use  for  heating  the  combustion  tube  in  the  deter- 
mination of  nitrogen.  The  arrangement  of  the  heating  sections 
and  the  heat  control  should  be  the  same  as  described  for  the 
carbon  and  hydrogen  combustion  (p.  230). 


284          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

NOTE 

Water  formed  in  the  reaction  sometimes  collects  in  the  end  of 
the  combustion  tube  near  the  azotometer,  especially  if  an  extra  long 
extension  is  used.  Since  the  water  is  not  needed  no  provision  is 
made  for  getting  rid  of  it.  However,  if  it  is  allowed  to  collect,  it 
will  cause  some  combustion  tubes  to  crack.  In  order  to  keep  it 
from  flowing  back  along  the  heated  portion  of  the  tube  and  causing 
the  tube  to  crack,  the  tube  may  be  slanted  somewhat  by  blocking 
up  the  other  end  of  the  furnace  2-3  cm.  above  the  level  of  the  desk. 

4.  The  Combustion  Tube  and  How  to  Fill  It. — The  com- 
bustion tube  itself  should  be  the  same  in  every  way  as  the  one 
described  in  connection  with  the  determination  of  carbon  and 
hydrogen  (pp.  232-3). 

The  method  of  filling  is  indicated  in  the  general  diagram 
(p.  276).  An  8-cm.  roll  of  cupric  oxide  gauze  (see  p.  235)  is  pre- 
pared and  placed  at  A ,  near  the  end  to  which  the  U-tube  is  con- 
nected. It  serves  the  same  purpose  as  the  one  in  the  carbon 
and  hydrogen  combustion,  that  is,  mainly  as  an  "  oxidation 
buffer  "  in  preventing  any  gases  which  may  go  backward  from 
getting  so  far  back  that  the  determination  is  spoiled  (see  p.  235). 

About  25  cm.  from  this  same  end  of  the  combustion  tube,  place 
a  short  roll  of  copper  gauze,  fitting  snugly;  follow  this  with  a 
layer  of  cupric  oxide  1  in  wire  form,  and  keep  this  in  place  with 
another  snugly  fitting  short  roll  of  copper  gauze.  This  entire 
layer,  including  the  short  "  spirals  "  should  measure  approxi- 
mately 26  cm.  The  open  space,  B,  between  the  long  cupric 
oxide  "  spiral  "  and  the  long  layer  of  cupric  oxide,  is  reserved  for 
the  boat. 

For  the  far  end  of  the  combustion  tube  which  is  heated  by 
section  No.  3,  prepare  a  12 -cm.  roll  of  copper  gauze,  D.  This  is 
always  used  in  the  reduced  condition  in  order  that  any  oxides 
of  nitrogen  that  may  be  formed  will  be  converted  into  elemental 

1  Cupric  oxide,  which  has  been  used  for  the  determination  of  carbon  and  hydro- 
gen, can  be  used  for  the  determination  of  nitrogen,  although  the  opposite  is  not 
the  case  on  account  of  the  possible  retention  of  carbon  dioxide,  unless  it  has  been 
heated  in  the  open  for  a  long  time  and  allowed  to  cool  in  the  air.  The  cerium 
dioxide  catalyst  cannot  be  used  in  the  nitrogen  determination. 


ORGANIC  COMBUSTIONS  285 

nitrogen  before  passing  into  the  azotometer.  The  reduction  is 
carried  out  as  follows:  Select  a  Pyrex  test-tube  of  such  a  size 
that  the  roll  of  copper  gauze  will  fit  in  it  loosely.  Place  a  wad 
of  asbestos  or  glass  wool  at  the  bottom,  add  not  more  than 
i  cc.  of  methyl  alcohol,  and  support  it  in  a  stand.  Heat  the 
spiral  to  redness  over  a  Meker  burner  or  in  a  very  large  blast 
flame.  In  order  to  avoid  melting  the  copper  the  lower  end  of  the 
spiral  is  slowly  swung  to  and  fro  while  the  upper  end  is  securely 
held  in  its  position  by  the  little  loop  with  a  pair  of  tongs.  In 
this  way  the  entire  gauze  is  evenly  heated.  Then  quickly  drop 
it  into  the  test-tube,  and  ignite  the  issuing  vapors.  Do  not 
breathe  the  fumes,  since  they  consist  largely  of  formaldehyde. 
If  the  heating  has  been  done  properly  the  copper  soon  looks 
beautiful  in  the  reduced  condition.  When  the  flame  dies  down 
and  just  as  it  recedes  into  the  tube,  put  in  the  cork  loosely,  and 
set  aside  until  it  becomes  cold  before  placing  the  spiral  into  the 
combustion  tube.  If  the  tube  is  not  stoppered,  the  hot  spiral 
will  be  reoxidized  as  air  follows  the  flame  down  the  tube. 

5.  The  Azotometer.1 — The  nitrogen  is  collected  and  measured 
in  a  SchifT  azotometer.2  It  is  illustrated  in  the  general  diagram 
on  p.  276,  and  as  shown  it  consists  of  a  graduated  tube  sur- 
mounted with  a  stop-cock  and  extension  cap,  and  near  the  bottom 
arranged  as  indicated  for  a  gas  inlet  protected  by  mercury  and  a 

1  The  term  "  azotometer  "  is  used  instead  of  "  nitrometer,"  as  the  apparatus 
is  sometimes  called,  since  the  latter  refers  more  directly  to  the  measurement 
of  nitric  oxide  formed  in  the  analysis  of  nitric  acid  by  reduction  with  mercury 
in  presence  of  sulfuric  acid,  while  azotometer  literally  means  the  nitrogen  measure. 
(French,  azote;  Greek,  utrpov  (metron)).    Schiff  speaks  of  it  in  his  original  article, 
Zeit.  anal.  Chem.,  7  (1868),  430,  as  an  "  azotometer."    Lunge,  Ber.,  11  (1878), 
434,  named  his  nitrometer  from  the  fact  that  he  desired  it  for  analyzing  "  nitrose," 
which  is  defined  by  Patterson  in  his  "  German-English  Dictionary  for  Chemists  " 
as  "  a  solution  of  nitrosylsulfuric  acid  in  sulfuric  acid,  formed  in  the  lead-chamber 
process."    This  material  is  known  in  English  as  "  nitrous  vitriol  "  and  described 
in  the  "  Century  Dictionary  "  as  "  strong  sulfuric  acid  charged  with  nitrosulphonic 
acid.     It  runs  off  from  the  bottom  of  the  Gay-Lussac  absorbing  tower  in  the  man- 
ufacture of  sulfuric  acid  by  the  lead-chamber  process."     Lunge  also  mentions 
"  Gay-Lussac-Thurm-saure "    (Gay-Lussac   tower  acid).     Compare   also  Lunge, 
"  Technical  Methods  of  Analysis,"  trans,  by  Keane  (1908),  Vol.  I,  Pt.  I,  125  and 
131- 

2  Schiff,  Zeit.  anal.  Chem.,  7  (1868),  430. 


286          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

connection  by  means  of  a  rubber  tube  to  a  reservoir  which  holds 
the  solution  of  potassium  hydroxide.  An  adjustable  ring  (not 
shown  in  the  diagram)  is  attached  for  holding  the  reservoir  in 
any  position  desired.  The  tube  proper  should  be  about  7-8  mm. 
inside  diameter,  48  cm.  long  (measured  from  the  reservoir  outlet 
to  the  stop-cock)  with  a  capacity  of  50  cc.  of  gas  and  gradu- 
ated in  one-tenths.  Enough  mercury  (about  10  cc.  or  135 
grams)  should  be  put  into  the  bottom  to  make  a  good  seal  for 
the  inlet  tube  1  but  not  enough  to  splash  over  into  the  tube  lead- 
ing to  the  reservoir.  The  distance  between  these  inlet  and 
outlet  tubes  should  be  not  less  than  3  cm.  Furthermore  the  inlet 
tube  should  be  bent  upwards  to  such  an  extent  (about  8  cm.) 
that  the  mercury  will  not  run  over  when  the  reservoir  full  of  KOH 
solution  is  raised  to  the  top  of  the  azotometer. 

Some  azotometers  are  made  without  the  cup  sealed  on  top, 
but  have  a  narrow  tube  for  connecting  with  a  eudiometer  for 
transferring  the  gas.  A  cup  can  be  put  on  one  of  this  type 
by  attaching  a  wide  tube  by  means  of  a  rubber  stopper.  Some  azo- 
tometers are  provided  with  water  jackets,  but  it  does  not  appear 
necessary  to  use  this  for  general  work. 

The  stop-cock  should  be  well  ground  and  all  directions  given 
for  handling  stop-cocks  should  be  used  in  handling  this  part 
of  the  azotometer  (see  pp.  229  and  283).  Be/ sure  that  all 
parts  of  both  key  and  barrel  are  dry  before  putting  on  the 
grease.  Except  when  the  apparatus  is  actually  in  use  the  key 
of  the  stop-cock  should  not  be  allowed  to  remain  in  its  proper 
position,  since  it  is  very  likely  to  become  "  frozen  "  even  on 
standing  overnight  if  there  is  any  of  the  potassium  hydroxide 
solution  in  the  grease.2  Attach  it  with  a  piece  of  twine. 

1  Dennstedt  in  his  "  Anleitung  zur  vereinfachten  Elementaranalyse,"  3  Auflage, 
125-8,  describes  a  modified  azotometer  which  has  a  capillary  inlet  tube  ending  in  an 
internal  projection  which  delivers  a  fine  stream  of  gas,  and  which  also  has  an  en- 
larged portion  below  the  graduated  part  to  serve  as  a  reservoir  in  case  a  large 
amount  of  gas  is  suddenly  delivered  into  the  azotometer. 

2  An  excellent  method  of  removing  "  frozen  "  stop-cocks  is  given  by  V.  C. 
Allison,  Journ.  Ind.  and  Eng.  Chem.,  11  (1919),  468.     The  handle  of  the  key  is 
slipped  into  a  socket  in  a  block  of  hard  wood  while  the  opening  of  the  block  rests 
as  a  collar  on  the  shoulder  of  the  barrel  of  the  stop-cock.     A  plug  of  wood  is  placed 
against  the  other  end  of  the  key,  and  easy  regular  pressure  brought  to  bear  by 


ORGANIC  COMBUSTIONS  287 

The  potassium  hydroxide  1  solution  is  prepared  by  dissolving 
100  grams  of  solid  potassium  hydroxide  in  100  cc.  of  water. 
Since  much  heat  is  developed  a  porcelain  or  quartz  casserole 
should  be  used.  The  solution  should  be  clear  and  free  from 
foreign  particles.  It  can  be  filtered  through  an  ordinary  wet 
fluted  2  filter  paper  if  the  solution  is  added  slowly.  The  amounts 
given  are  sufficient  for  the  azotometer  described  above,  and  are 
enough  for  at  least  two  "  runs."  The  solution  may  become  col- 
ored from  contact  with  the  rubber  tubing  but  this  seems  to  do 
no  harm. 

The  mercury  can  be  purified  by  washing,  and  then,  after 
removing  most  of  the  water,  filtering  it  through  a  dry  filter  paper 
containing  a  few  tiny  holes  in  the  bottom.  Repeat  several  times 
if  necessary. 

Testing  the  Azotometer. — Clean  it  thoroughly,  properly 
grease  the  stop-cock,  and  add  the  mercury  and  the  potassium 
hydroxide  solution.  Attach  stop-cock  No.  6,  open  it  and  also 
No.  7,  the  one  on  the  azotometer  (see  general  t diagram,  p.  276). 
Lift  up  the  reservoir  slowly  from  position  I  to  position  II,  and  note 
the  rise  of  the  mercury  in  the  inlet  tube.  It  should  not  go  into 
the  tube  of  the  stop-cock,  although  this  will  do  no  particular 
harm,  but  it  should  never  go  beyond  the  stop-cock.  Lower  the 
reservoir  until  there  is  4-5  cc.  of  air  in  the  tube,  then  close  the 
stop-cock  (No.  7).  Now  lower  the  reservoir  to  position  I  and 
after  allowing  two  to  three  minutes  for  drainage  take  the  reading 
and  record  it.  Allow  the  apparatus  to  stand  for  twenty  to 
thirty  minutes,  take  the  reading  under  the  same  conditions, 
and  compare  with  the  previous  reading.  If  there  is  no  decided 
change  and  no  chance  for  temperature  fluctuation,  the  stop- 
cock is  tight,  but  if  the  volume  has  increased  there  is  something 
wrong  with  the  stop-cock  or  with  the  greasing. 

means  of  a  vise.     Different  sizes  are  given  for  the  ordinary  stop-cocks  in  use.    The 
scheme  is  rapid  and  it  works! 

1  Sodium  hydroxide  cannot  be  used,  since  the  carbonates  formed  crystallize  out 
and  cause  much  trouble. 

2  See  foot  note,  p.  128. 


288          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

V.  The  Final  Preparation  of  the  Cupric  Oxide  l 

Cupric  oxide  when  heated  and  cooled  in  an  atmosphere  of 
oxygen  or  air  adsorbs  some  of  these  gases.     The  cupric  oxide  thus 

1  NOTES  AND  REFERENCES 

Cupric  oxide  has  been  used  in  organic  combustions  for  the  determination  of 
carbon  and  hydrogen  and  nitrogen  since  1815  (see  p.  218),  and  the  method  for 
determining  nitrogen  separately  was  worked  out  especially  by  Dumas  in  1831  (see 
p.  269).  That  cupric  oxide  absorbs  gases  and  gives  them  up  on  heating  was  noticed 
as  early  as  1842,  when  Erdmann  and  Marchand,/./«>  prakt.Chcm.,2.Q  (184 2), 466-7, 
working  "  On  the  atomic  weight  of  hydrogen,"  showed  that  100  grams  of  cupric 
oxide  when  heated  in  an  atmosphere  of  carbon  dioxide  after  "  pure  carbonic  acid  " 
had  been  passed  through  the  tube  for  many  hours,  gave  5.5.  cc.  of  air  unabsorbed 
by  potassium  hydroxide  solution.  In  1868  Frankland  and  Armstrong,  in  an 
article  "  On  the  Analysis  of  Potable  Waters,"  /.  Chem.  Soc.,  21  (1868),  89  and  93, 
described  their  method  of  determining  carbon  and  nitrogen  in  very  small  amounts 
of  organic  material  by  burning  it  in  a  combustion  tube  after  complete  evacuation 
with  a  Sprengel  pump  and  analyzing  the  gases  evolved.  They  state,  "  Cupric 
oxide  prepared  from  the  nitrate  should  on  no  account  be  used,  since,  even  after 
being  actually  fused,  it  evolves  considerable  quantities  of  carbonic  anhydride  and 
nitrogen  when  ignited  in  vacuo."  Eight  years  later  Thudichum  and  Kingzett, 
/.  Chem.  Soc.,  30  (1876),  363,  confirmed  these  findings  in  general.  Hilditch, 
Chem.  News,  49  (1884),  37,  mentions  the  fact  that  cupric  oxide  occludes  air,  and 
Morley,  Amer.  J.  Sci.,  41  (1891),  281,  shows  that  cupric  oxide  slowly  gives  off 
gas  in  a  vacuum.  T.  W.  Richards,  in  revising  the  atomic  weight  of  copper,  Proc. 
Amer.  Acad.  Arts  and  Sci.,  26  (1891),  281,  and  Zcit.  anorg.  Chem.,  1  (1892),  196; 
proved  that  several  of  the  formerly  accepted  results  were  incorrect  on  account  of 
the  error  involved  due  to  gas  adsorbed  by  the  cupric  oxide  which  had  been  used  for 
the  determinations.  In  his  later  systematic  work  on  this  particular  subject,  "  On 
the  Cause  of  the  Retention  and  Release  of  Gases  occluded  by  the  Oxides  of 
Metals,"  Amer.  Chem.J.,2Q  (1898),  701,  he  states  (page  711),  "When  the  im- 
prisoned gas  (in  cupric  oxide)  has  once  begun  to  be  set  free,  at  temperatures  above 
850°,  the  time  is  an  essential  factor,  and  that  when  sufficient  time  has  been  allowed, 
the  expulsion  of  the  gas  is  almost  complete."  Furthermore  (p.  727),  "  Two  grams 
of  cupric  oxide,  which  had  been  ignited  for  a  long  time  in  pure  air  until  constant 
in  weight,  were  found  to  evolve  a  gas  steadily  when  heated  in  a  vacuum  to  about 
the  melting-point  of  common  salt  (790°),  provided  that  the  gas  was  removed  by 
a  Sprengel  pump  as  fast  as  it  was  formed."  Cupric  oxide  begins  to  lose  "  struc- 
tural oxygen  "  even  in  the  air  at  about  1000°,  but  this  is  above  the  melting-point 
of  the  hard  glass  used.  Cuprous  oxide  was  found  in  the  residue.  The  observation 
is  then  made  (p.  728): 

"  Since  cupric  oxide  is  slightly  dissociated  by  heat,  perceptible  amounts  of 
oxygen  should  be  removed  by  heating  it  in  nitrogen,  just  as  carbonic  acid  is  removed 
from  limestone  by  heating  it  in  a  current  of  air.  This  dissociation  of  cupric  oxide 
must  have  its  effect  on  any  process  involving  the  ignition  of  cupric  oxide  in  a 
vacuum  or  in  an  inert  gas.  The  determination  of  organic  nitrogen  by  means  of  the 
Sprengel  pump,  for  example,  must  be  affected  by  it.  The  use  of  carbon  dioxide 


ORGANIC  COMBUSTIONS  289 

prepared  on  being  heated  again  slowly  gives  off  the  adsorbed  gas. 
Since  the  gas  which  is  slowly  given  off  is  not  absorbed  by  the 

as  a  displacing  medium  in  the  Dumas  method,  probably  disposes  of  the  error, 
however,  for  carbon  dioxide  is  itself  dissociated  by  heat,  and  it  undoubtedly  fur- 
nishes enough  oxygen  to  diminish  greatly  the  decomposition  of  the  cupric  oxide." 
(NOTE. — It  should  be  emphasized  that  this  latter  statement  refers  only  to 
the  liberation  of  gas  from  the  actual  decomposition  of  the  cupric  oxide  and  not 
to  the  liberation  of  occluded  gases.) 

The  gas  occluded  in  the  cupric  oxide  is  only  slowly  given  off  by  heating  to 
redness,  and  the  error  involved  in  the  nitrogen  determination  amounts  to  +0.2  to 
0.5  per  cent l  (usually  nearer  the  higher  figure)  when  0.2  gram  of  the  sample  is 
used.  Diminishing  the  time  of  the  combustion  of  course  diminishes  this  error, 
and  usually  there  are  compensating  errors,  which  vary  a  great  deal,  in  general 
practice  which  also  sometimes  keep  the  final  error  down  to  the  ordinary  amount, 
that  is,  0.2  per  cent.  When  a  substance  with  a  high  content  of  nitrogen  is  analyzed 
the  "  percentage  error  "  is  of  course  decreased,  but  with  a  low  content  of  nitrogen 
it  is  very  serious.  None  of  the  text-books  on  practical  organic  chemistry  to  which 
one  would  ordinarily  go  for  a  description  of  the  Dumas  method,  such  as  those  by 
Gattermann,  W.  A.  Noyes,  and  J.  B.  Cohen,  say  anything  about  this  error, 
Neither  is  it  mentioned  by  Clarke,  "  A  Handbook  of  Organic  Analysis;"  King- 
scott  and  Knight,  "  Quantitative  Organic  Analysis;  "  nor  even  by  Lassar-Cohn 
"  Arbeitsmethoden,"  allgemeine  Teil,  4  Auflage  (1906);  and  Weyl,  "  Die  Method- 
en  der  organischen  Chemie,"  allgemeine  Teil  (1909).  All  these  authors  do 
generally  speak  of  the  "  minimum  amount  of  foam  "  that  always  collects  in  the 
top  of  the  azotometer  and  which  Thudichum  and  Kingzett,  /.  Chem.  Soc.,  30 
(1876),  366,  characterized  as  "  that  obstinate  bubble  in  the  gas-tube  which  has  puzzled 
so  many  of  the  best  experimentalists" 

In  1915  Fieldner  and  Taylor,  /.  Ind.  and  Eng.  Chem.,  7  (1915),  106,  attempted 
to  check  up  their  results  of  the  analysis  of  some  samples  of  coal  for  nitrogen,  made 
by  modifications  of  the  Kjeldahl  method,  with  the  Dumas  method  since  "it  is 
generally  regarded  as  fundamental  and  applicable  to  most  classes  of  organic  com- 
pounds." Since  the  coal  contained  only  very  small  amounts  of  nitrogen,  approxi- 
mately i  per  cent,  they  naturally  tested  their  apparatus  and  method,  as  given  in 
the  usual  references,  by  blank  runs,  and  found  what  many  others  have  also  found, 
that  varying  amounts  of  gas  were  given  off,  for  example,  6.6  cc.  after  six  hours' 
heating  followed  by  1.4  cc.  when  the  tube  was  re-heated  the  next  day.  They  then 
noted  the  following  remarks  by  H.  Meyer  in  his  "  Analyse  und  Konstitutionsermit- 
telung  organischen  Verbindungen,"  2  Auflage  (1909),  187,  "  The  chief  source  of 
error  lies  in  the  impossibility  of  freeing  the  fine  copper  oxide  from  air,  and 
therefore  most  of  the  results  are  too  high  by  o.i  to  0.2  per  cent."  Also,  in  Fre- 
senius-Cohn,  "  Quantitative  Chemical  Analysis,"  6th  Ed.,  II  (1904),  68,  "The 
results  are  generally  somewhat  too  high,  viz.,  by  about  0.2  to  0.5  per  cent,"  and 
that  in  a  blank  experiment  with  sugar  the  quantity  of  unabsorbed  gas  "  should 
not  exceed  i  or  1.5  cc."  H.  N.  Morse,  "  Exercises  in  Quantitative  Chemistry" 
(1905),  provides  in  part  for  the  difficulty  by  heating  both  coarse  and  fine  cupric 
oxide  for  i|  hours  at  full  red  heat  in  a  current  of  oxygen  which  is  followed,  without 
1  F.  Blau,  Monatschefte,  13  (1892),  277. 


290          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

potassium  hydroxide  solution  in  the  azotometer.  it  causes  a 
serious  error  in  the  determination  of  nitrogen. 

To  prepare  the  cupric  oxide  for  the  analysis,  it  must  be 
heated  strongly  to  a  good  red  heat,  just  as  in  the  combustion 
itself,  in  a  vacuum  for  about  six  hours,  the  gases  being  removed 
and  replaced  by  "  flooding  "  the  apparatus  two  or  three  times 
with  pure  carbon  dioxide.  Finally  the  cupric  oxide  is  allowed  to 
cool  in  an  atmosphere  of  pure  carbon  dioxide.  In  this  manner 
the  gas  adsorbed  is  one  that  will  cause  no  trouble  in  the  analysis. 

After  the  entire  apparatus  1  is  set  up  and  the  generator 
properly  filled,  according  to  the  description  in  Chapter  IV,  p.  275, 
set  the  stop-cocks  as  follows:  Nos.  i,  2,  6  and  9  closed,  and 
3,  4,  5,  7,  8,  10,  and  n  open;  then  turn  on  the  pump,  and  also 
begin  the  heating.  It  is  not  necessary  that  the  heating  be  done 
without  interruption,  but  if  it  is  interrupted  the  cupric  oxide 
must  be  allowed  to  cool  in  an  atmosphere  of  carbon  dioxide, 
otherwise  little  will  have  been  accomplished. 

Soon  after  the  apparatus  has  been  evacuated,  occluded  and 

cooling,  by  carbon  dioxide  for  an  hour  or  more,  and  the  oxide  is  allowed  to  cool 
in  CO2.  Finally  in  an  obscure  journal,  in  an  article  published  in  1898  by  F.  C. 
Phillips,  on  the  "  Fluctuation  in  the  composition  of  Natural  Gas,"  Proc.  Eng.  Soc. 
Western  Pa.,  14,  299,  they  found  an  account  of  similar  difficulties  overcome:  "  In 
beginning  a  series  of  determinations  several  days  were  often  required  for  the  purpose. 
The  porcelain  tube  was  strongly  heated,  while  a  slow  stream  of  carbon  dioxide  was 
maintained;  the  CuO  was  not  considered  to  be  in  proper  condition  until  the 
escaping  CO2  was  absorbed  without  residue.  It  was  found  that  the  CuO  when 
once  impregnated  with  CO2,  while  strongly  heated,  could  be  reoxidized  by  air  cur- 
rent with  little  tendency  to  occulsion  of  air,  but  if  the  copper  oxide  was  allowed  to 
cool  in  contact  with  air  much  time  was  lost  in  removing  the  air  by  carbon  dioxide 
even  when  strong  heat  was  applied."  Fieldner  and  Taylor  then  proceeded  to 
shorten  the  time  for  the  final  preparation  of  the  cupric  oxide  by  heating  it  in 
vacua.  It  is  well  worth  one's  while  to  go  over  their  recorded  experiments  as 
given  in  their  original  article  mentioned  above.  They  concluded  that,  "  Errors  in 
the  Dumas  method  due  to  nitrogen  from  the  CuO  were  minimized  by  previously 
heating  the  oxide  for  several  hours  in  vacua,  cooling  it  in  CO2,  and  using  '  wire 
form  '  oxide  pulverized  to  pass  through  a  40-mesh  screen  and  remain  on  100  mesh." 
These  results  are  incorporated  in  the  present  work. 

xThe  boat  filled  with  CuO  wire  should  be  in  place  (p.  284),  but  the  reduced 
copper  spiral  should,  of  course,  not  be  in  the  tube  during  the  preliminary  heating 
(pp.  294-5).  Also,  it  is  not  absolutely  necessary  to  have  the  azotometer  attached 
at  this  time. 


ORGANIC  COMBUSTIONS  291 

dissolved  air  and  finally  some  CCb  will  begin  to  come  out  of  the 
materials  in  the  generator.  In  order  to  help  get  rid  of  as  much 
air  in  the  generator  as  possible,  allow  a  little  sulfuric  acid  to 
flow  into  the  carbonate  mixture.  After  the  vacuum  has  been 
maintained  for  about  half  an  hour,  close  No.  3  and  leave  the  gen- 
erator under  these  conditions  until  you  are  ready  to  flood  the 
apparatus  with  C02. 

To  flood  the  apparatus  with  C02:  Close  No.  10,  then  turn 
off  the  pump.  If  No.  3  has  been  closed  during  the  heating, 
gradually  open  it.  The  mercury  in  the  manometer  will  fall 
somewhat.  Now  allow  the  sulfuric  acid  to  flow  slowly  into  the 
carbonate  mixture.1  Carefully  watch  the  fall  of  the  mercury, 
and  when  the  two  columns  are  level  quickly  open  No.  2  in  order 
that  the  excess  of  C02  may  pass  out.  By  opening  No.  6  (leaving 
No.  7  open  also  if  the  azotometer  is  attached)  the  gas  can  sweep 
out  the  entire  apparatus.  Then  close  No.  6  and  No.  3,  turn  on 
the  pump,  and  open  No.  10,  and  continue  the  heating  as  before. 

When  the  six  hours'  heating  is  at  an  end,  flood  the  apparatus 
once  again  in  the  same  way  as  before,  making  certain  that  No.  2 
has  been  closed  before  No.  3  is  opened.  Now  turn  off  the  heat 
and  allow  the  cupric  oxide  to  cool  in  the  atmosphere  of  CCb. 
The  tube  may  be  left  alone  to  cool  after  closing  Nos.  5  and  6 
If  you  have  time,  pass  CO2  through  the  tube  while  it  is  cooling; 
but  this  is  probably  not  necessary.  When  you  leave  the  appa- 
ratus for  the  night,  see  that  Nos.  5,  6,  i,  2,  10,  and  n  are  closed; 
and  that  3,  8,  and  9  are  open. 

In  order  to  avoid  contaminating  the  carbon  dioxide  in  the 
generator  with  air  from  possible  leaks  when  the  generator  is 
under  diminished  pressure,  it  is  well  to  keep  it  under  a  little 
pressure  practically  all  the  time  and  especially  during  the  combus- 
tion, allowing  the  excess  to  pass  out  through  stop-cock  No.  2 
and  the  mercury  trap.  By  exercising  a  little  care  you  will  find  it 
possible  to  keep  the  generator  under  pressure  even  when  connect- 
ing it  with  the  apparatus  that  has  been  evacuated.  After  stop- 
cock No.  10  has  been  closed  and  while  a  good  stream  of  gas  is 

1  Too  much  acid  at  one  time  will  cause  the  mixture  to  foam  over  into  other 
parts  of  the  apparatus. 


292         LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

going  out  through  the  mercury  trap,  partially  open  stop-cock 
No.  3,  watching  the  overflow  all  the  time.  As  soon  as  the 
mercury  begins  to  rise  in  the  outlet  tube  close  stop-cock  No.  3, 
and  then  gradually  open  it  again.  Frequent  glances  at  the 
manometer  will  show  how  the  operation  is  going  on.  In  this 
way  the  apparatus  will  soon  be  filled  with  carbon  dioxide  and 
the  generator  always  kept  under  pressure  and  free  from  con- 
taminating air. 

After  the  cupric  oxide  has  been  heated  and  cooled  in  C02, 
it  can  be  handled  in  the  open  but  not  without  adsorbing  air  that 
will  cause  a  small  error.  For  example,  Fieldner  and  Taylor  1 
found  that  when  100  grams  of  the  cupric  oxide  "  was  subjected 
to  alternate  vacuum  and  carbon  dioxide  for  several  hours  at 
850°  C.,  until  no  further  nitrogen  was  evolved,  and  was  then 
cooled  in  C02,  exposed  to  air  and  again  heated,  the  40-100 
mesh  '  wire  '  oxide  gave  off  only  0.7-0.9  cc.  of  nitrogen,  while 
the  2oo-mesh  material  gave  off  1.9-2.2  cc." 

When  a  combustion  has  been  run  it  is  necessary  to  reoxidize 
some  of  the  copper,  and  have  it  ready  for  another  determination. 
Before  turning  off  the  heat  (or  after  allowing  to  cool  in  C02), 
remove  the  reduced  copper  spiral,  and  while  the  tube  is  hot  pass 
air  or  oxygen  through  it  until  all  the  copper  has  been  oxidized. 
Then  while  the  tube  is  still  hot,  replace  the  air  or  oxygen  with 
pure  CO2  in  the  usual  manner,  keeping  up  the  passage  of  the 
carbon  dioxide  for  an  hour,  and  allow  to  cool  in  the  atmosphere 
of  C02  while  the  tube  is  closed.  It  is  not  necessary  to  heat  again 
for  six  hours  as  is  the  case  when  the  cupric  oxide  has  been  cooled 
in  air 

VI.  Weighing  the  Substance 

The  substance  is  weighed  in  a  porcelain  or  quartz  boat  inside 
the  special  boat  tube  ("  piggie  ")  and  all  precautions  as  to 
moisture,  state  of  division,  etc.,  mentioned  in  connection  with 
weighing  the  substance  for  the  carbon  and  hydrogen  determina- 
tion must  be  observed  in  this  case  also  (see  p.  252).  After  the 
substance  has  been  weighed,  and  the  weight  recorded,  it  is  not 

1  Journ.  Ind.  and  Eng.  Chem.,  7  (1915),  in. 


^ORGANIC  COMBUSTIONS  293 

essential  in  most  cases  that  moisture  be  so  rigidly  excluded  as 
for  the  carbon  and  hydrogen  determination.  However,  it  is 
unfortunate  for  one  to  let  down  on  the  good  practice  of  keeping 
moisture  from  weighed  samples,  and  thus  spoil  a  good  habit. 

The  amount  of  substance  used  should  ordinarily  be  about 
0.2000  gram.  If  the  nitrogen  content  is  approximately  known, 
use  enough  substance  to  give  about  15-20  cc.  of  nitrogen.  Some 
substances  have  a  high  percentage  of  nitrogen,  and  0.2  gram 
would  give  more  nitrogen  than  the  azotometer  could  hold.  Then 
the  amount  of  sample  should  be  cut  down  accordingly.  Cor- 
respondingly, the  amount  of  sample  of  a  substance  with  a  very  low 
content  of  nitrogen  should  be  increased,  even  to  0.5  gram,  if 
necessary,  and  provided  this  much  can  be  spared. 

VII.  General  Method  of  Procedure  for  the  Combustion  Proper 

Testing  the  Apparatus. — After  the  cupric  oxide  has  been 
prepared  and  the  tube  filled  with  carbon  dioxide  as  already 
described  (p.  288),  test  out  the  entire  apparatus  to  see  if  the 
cupric  oxide  is  all  right,  the  carbon  dioxide  is  pure  enough,  and 
all  joints  are  in  good  condition.  Have  all  of  the  apparatus  con- 
nected and  heat  the  combustion  tube  as  for  a  regular  combustion. 
Pass  carbon  dioxide  through  it  and  into  the  azotometer  for  five 
to  ten  minutes.1  In  order  not  to  exhaust  the  potassium  hydrox- 
ide solution,  drop  the  reservoir  to  position  I,  and  have  stop-cock 
No.  7  in  the  azotometer  open.  At  the  end  of  the  time  specified, 
while  the  gas  is  still  passing,  carefully  raise  the  reservoir  to  posi- 
tion II  when  the  solution  will  flow  through  the  stop-cock  and 
into  the  cup  on  top.  Now  close  the  stop-cock  and  slowly  lower 
the  reservoir  to  its  former  position  in  order  to  reduce  the  pres- 
sure against  the  inflowing  gas.  Pass  the  gas  through  at  a  fair 
rate  for  about  five  minutes.  The  bubbles  should  not  be  so  large 
and  come  so  fast  that  they  fill  the  entire  azotometer  tube  and  force 
all  the  potassium  hydroxide  solution  into  the  reservoir.  After 
the  five  minutes  note  whether  the  volume  of  unabsorbed  gas 
which  collects  at  the  top  is  more  than  o.i  cc.  It  is  difficult  to 

1  In  order  to  take  care  of  any  excess  of  pressure  in  the  generator,  be  sure  to  have 
stop-cock  No.  2  open  (see  p.  277). 


294          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

formulate  any  rule  for  how  much  unabsorbed  gas  should  be 
allowed,  since  the  rate  varies,  etc.,  but  if  much  gas  collects,  then 
the  stop-cock  (No.  7)  should  be  opened  again  to  let  the  solution 
flow  down  and  carbon  dioxide  run  through  freely  for  another 
five  minutes,  and  a  second  trial  made  for  almost  complete  ab- 
sorption as  before.  If  the  gas  is  not  passing  too  rapidly  the  bub- 
bles diminish  to  the  size  of  pin-points  as  they  float  upward.  If 
much  unabsorbed  gas  is  collected  again  either  the  cupric  oxide 
has  not  been  properly  prepared  or  the  generator  and  joints  leak 
or  the  carbonate  is  impure,  and  these  must  be  attended  to. 
This  operation  shows  the  chief  error  involved  in  the  determination 
of  nitrogen  and  therefore  the  error  in  the  final  result  will  be  in 
almost  direct  relation  to  the  amount  of  gas  unabsorbed  in  these 
blank  tests. 

If  there  is  any  doubt  as  to  the  proper  condition  of  the  appara- 
tus a  complete  blank  run  should  be  carried  out,  using,  for  example, 
0.2  gram  of  sucrose  (cane  sugar)  in  place  of  a  nitrogenous  sub- 
stance. 

When  the  test  is  satisfactory  let  that  part  of  the  combustion 
tube  which  is  to  contain  the  boat,  and  several  centimeters  each 
side  of  it,  cool  down  to  room  temperature.  During  the  cooling 
reduce  the  rate  of  the  carbon  dioxide,  or  close  stop-cocks  Nos.  5 
and  6  to  prevent  any  of  the  potassium  hydroxide  solution  from 
being  drawn  into  the  combustion  tube.  If  a  combustion  is  not 
to  be  made  immediately,  let  the  entire  tube  cool  down  in  an 
atmosphere  of  carbon  dioxide  (see  p.  291). 

The  Combustion. — The  following  arrangements  are  made 
for  beginning  the  combustion  proper  depending  upon  whether 
the  furnace  is  cold  or  heated  in  part: 

a.1  If  the  furnace  is  cold,  disconnect  both  ends  of  the  com- 
bustion tube,  carefully  remove  the  cupric  oxide  spiral, 
insert  the  boat  containing  the  substance,2  replace  the  cupric 

b.      oxide  spiral,  and  then  insert  the  cold  reduced  copper  spiral 

1  These  letters  in  the  margin  refer  to  the  corresponding  parts  in  the  Topical 
Outline,  section  n,  p.  273. 

2  If  the  substance  burns  with  difficulty  it  should  be  covered  with  some  of  the 
cupric  oxide  wire  already  prepared  for  this  purpose  (p.  290). 


ORGANIC  COMBUSTIONS  295 

in  the  position  reserved  for  it  beyond  the  layer  of  cupric 

c.  oxide.     Connect  up  the  apparatus  again,  remove  the  air 
by  evacuation  and  flood  with  pure  CO2  by  the  usual  proce- 

d.  dure.     While  the  reservoir  of  the  azotometer  is  in  position 
I  and  stop-cocks  Nos.  6  and  7  are  open,  and  carbon  dioxide 
is  slowly  passing  through  the  apparatus,  heat  the  reduced 
copper  spiral  to  redness  in  order  to  drive  out  any  occluded 
gases,  such  as  hydrogen  and  air,  and  then  heat  the  adjacent 
cupric  oxide,  making  certain  that  the  substance  in  the 
boat  is  not  heated  at  all.     This  can  be  done  if  the  long 
heating  section,  No.  2,  is  pushed  over  toward  the  reduced 
spiral  (see  general  diagram,  p.  276). 

e.  While  the  tube  is  thus  being  heated,  test  the  apparatus 
to  see  if  the  amount  of  unabsorbed  gas  is  at  a  minimum,  as 

/.  described  at  the  beginning  of  this  chapter.  If  the  sub- 
stance decomposes  readily  the  heating  of  the  cupric  oxide 
should  be  delayed  until  after  the  final  test. 

If  the  combustion  tube  has  been  heated,  and  only  that  part 
which  is  to  contain  the  boat  and  several  centimeters  on  each 
side  of  it  including  the  cupric  oxide  spiral  have  been  allowed 
to  cool  down  practically  to  room  temperature,  then,  in  order 
to  make  the  final  preparations,  disconnect  both  ends  of  the 
combustion  tube,  carefully  remove  the  cupric  oxide  spiral, 

a  insert  the  boat  containing  the  substance,1  and  quickly 
replace  the  spiral.  Connect  up  this  end  only,  leaving 
the  other  end  open,  and  pass  CCb  rapidly  through  the  tube. 
When  you  are  reasonably  certain  that  the  air  has  been 

b.  driven  out,  insert  the  cold  reduced  copper  spiral  into  the 

c.  heated  part  of  the  tube  and  quickly  connect  the  azotometer, 
making  sure  beforehand  that  stop-cocks  Nos.  6  and  7  are 

d.  open  and  the  reservoir  is  in  low  position  I.     In  this  way 
the  reduced  spiral  will  not  become  oxidized,  provided  there 
is  a  good  flow  of  CO2.     Any  occluded  gases  in  the  reduced 
spiral  will  be  driven  out  in  about  five  minutes  of  strong 

e.  heating.     Now  test  the  apparatus  to  see  if  the  amount  of 

1  As  stated  above,  if  the  substance  burns  with  difficulty  it  should  be  covered 
with  some  of  the  cupric  oxide  wire  already  prepared  for  this  purpose  (p.  290). 


296          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

unabsorbed  gas  is  at  a  minimum,  as  described  at  the  be- 
ginning of  this  chapter. 

/.  It  must  be  borne  in  mind  that  these  preliminary  opera- 

tions should  be  varied  in  accordance  with  the  properties 
of  the  substance.  If  it  has  a  high  vapor  pressure  and  sub- 
limes readily  or  is  easily  melted,  the  time  factor  must  be 
reduced,  the  heating  regulated,  etc.  Furthermore,  it 
cannot  be  overemphasized  that  good  judgment  and  familiar- 
ity with  the  method  are  always  very  necessary  to  give  reliable 
results. 

As  soon  as  it  has  been  found  that  the  amount  of  un- 
absorbed gas  has  been  reduced  to  the  proper  minimum 

g.  amount,  reduce  the  flow  of  carbon  dioxide  to  such  an  extent 
that  it  will  just  keep  the  products  of  combustion  moving 
toward  the  azotometer,  using  the  stopper  (No.  5)  in  the 
U-tube  for  regulating  the  gas,  and  allowing  the  excess  of 
carbon  dioxide  in  the  generator  to  escape  regularly  through 
stop-cock  No.  2  and  the  safety  bottle. 

Raise  up  the  reservoir  and  when  it  is  opposite  the  stop- 
cock (No.  7),  open  the  stop-cock  to  allow  the  small  amount  of 
unabsorbed  gas  that  may  have  collected  to  pass  out,  care- 
fully close  the  stop-cock,  leaving  some  of  the  solution  in  the 
cup  above,  and  lower  the  reservoir  to  position  I.  If  there 
has  been  any  indication  that  the  substance  has  begun  to 
decompose  then  the  small  amount  of  unabsorbed  gas  should 
not  be  driven  out  of  the  azotometer  lest  some  nitrogen  from 
the  substance  be  driven  out  too. 

h.  Now  gradually  heat  more  of  the  cupric  oxide  by  drawing 

the  long  heating  section  (No.  2)  toward  the  boat  a  centi- 
meter at  a  time,  and  at  the  same  time  begin  to  heat  slowly 
the  cupric  oxide  spiral  on  the  other  side  of  the  boat  with 
section  No.  i. 

As  mentioned  in  connection  with  the  carbon  and  hydro- 
gen determination  (p.  254),  it  is  very  difficult  to  describe 
in  detail  the  actual  method  of  burning  the  substance,  since 
each  one  has  its  own  peculiarities,  and  therefore  only  a 


ORGANIC  COMBUSTIONS  297 

general  description  can  be  given.  Here  also  an  idea  as  to 
how  the  substance  behaves  on  heating  should  be  gained 
beforehand,  if  sufficient  is  available,  by  heating  it  and 
gradually  burning  it  in  a  boat  over  a  small  flame.  Notice 
whether  it  gradually  burns,  sublimes,  or  suddenly  decom- 
poses. 

The  substance  is  slowly  burned  by  gradually  drawing 
the  two  adjacent  sections  closer  and  closer  in  alternate  turns 
toward  the  boat.  When  the  large  heating  section  (No.  2) 
is  over  all  the  cupric  oxide  do  not  draw  it  any  further.  Use 
the  small  heating  section  (No.  i)  to  heat  and  slowly  and  com- 
pletely decompose  the  substance  in  the  boat.  Since  the 
substance  chars  and  the  carbon  is  not  completely  burned  in 
the  presence  of  carbon  dioxide,  the  amount  and  appear- 
ance of  the  black  deposit  does  not  give  a  very  good  indica- 
tion of  the  course  of  the  combustion.  But  the  amount  of 
gas  which  enters  the  azotometer,  and,  passing  upward,  is 
only  partially  absorbed,  does  give  a  good  idea  as  to  how  the 
combustion  is  progressing.  The  gas  should  not  come 
through  so  fast  that  the  bubbles  will  be  very  large  and 
rapidly  fill  the  azotometer  tube,  since  there  is  danger  that 
all  the  potassium  hydroxide  solution  will  be  driven  over  into 
the  reservoir  and  then  the  gas  will  follow ! 

After  about  twenty  minutes  the  substance  will  all  be 
decomposed  and  the  rate  of  the  gas  entering  the  azotometer 
will  then  decrease  to  that  of  the  carbon  dioxide  itself. 
i.  Now  drive  over  the  remaining  nitrogen  with  carbon  dioxide 
by  gradually  increasing  the  flow  of  the  latter,  and  continue 
this  until  the  bubbles  of  unabsorbed  gas  are  very  tiny  just 
as  was  noticed  before  the  combustion  was  begun.  If  the 
volume  of  nitrogen  in  the  azotometer  is  large  the  bubbles 
will  not  have  very  much  liquid  through  which  to  travel 
and  on  this  account  it  is  sometimes  not  so  easy  to  make  a 
proper  comparison.  In  such  a  case  the  gas  is  run  through 
for  about  ten  minutes  after  it  appears  that  all  the  nitrogen 
has  been  driven  over. 
j.  Then  close  stop-cock  No.  6  (between  the  azotometer  and 


298          LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

the  combustion  tube),  and  wash  the  nitrogen  in  the  azo- 
tometer  with  one  portion  of  the  potassium  hydroxide  solu- 
tion. This  is  done  while  the  reservoir  is  in  the  low  position 
(I),  the  stop-cock  being  carefully  and  partially  opened  to 
allow  the  solution  to  run  easily  down  the  inside  walls  to 
absorb  any  traces  of  carbon  dioxide  that  may  be  present, 
and  closed  before  all  the  solution  has  left  the  cup.  Now 
wash  the  gas  in  a  similar  manner  with  successive  portions 
of  cold  distilled  water  which  has  been  recently  boiled  to 
drive  out  dissolved  air,1  until  all  the  potassium  hydroxide 
solution  is  out  of  the  azotometer  and  the  reservoir  also. 
Always  keep  some  liquid  in  the  cup.  While  the  washing  is 
being  done  do  not  let  the  potassium  hydroxide  solution  over- 
flow. It  should  be  poured  out  and  saved  for  a  second 
combustion  unless  it  is  "  spent,"  and  when  you  pour  it  out 
be  sure  not  to  pour  all  of  it  at  a  time,  since  air  may  get 
into  the  rubber  tube  and  then  into  the  azotometer! 

k.  Raise  up  the  reservoir  until  the  liquid  in  it  is  on  a  level 

with  the  liquid  in  the  azotometer  in  order  that  the  nitrogen 
will  remain  at  atmospheric  pressure,  thus  preventing  any 
error  from  leakage,  etc.,  and  clamp  the  holder  of  the  reser- 
voir in  this  position.  Place  a  thermometer  in  some  water  in 
the  cup  above,  or  hang  it  beside  the  azotometer,  and  allow 
the  apparatus  to  remain  untouched  in  a  room  of  uniform 
temperature  for  at  least  twenty  to  thirty  minutes.  Then 
record  the  volume  of  the  gas,  as  read  by  the  bottom  of 
the  meniscus,  the  temperature,  and  also  the  barometric 
reading  and  the  temperature  of  the  barometer. 

/.  From  these  results  and  the  weight  of  i  cc.  of  moist 

nitrogen  (given  in  milligrams)  as  found  in  the  accompanying 
tables,  for  the  proper  temperature  and  pressure,  you  can 
calculate  the  weight  of  nitrogen  obtained  and  then  the  per- 
centage of  nitrogen  in  the  substance  (see  section  on  Cal- 
culations, p.  300). 

1  Otherwise  this  air  will  be  liberated  when  the  water  mixes  with  the  potassium 
hydroxide  solution  which  does  not  dissolve  as  much  air  as  water  does. 


ORGANIC  COMBUSTIONS  299 


NOTES 

1.  Some  operators  prefer  to  measure  the  nitrogen  over  the  potas- 
sium hydroxide  solution.     The  weight  of  the  nitrogen  is  different 
from  what  it  is  when  measured  over  water  on  account  of  the  differ- 
ence in  vapor  pressure  of  the  two  liquids.     One  of  the  difficulties, 
however,  in  reading  the  volume  over  the  alkaline  solution  is  that  it 
is  practically  impossible  to  get  rid  of  the  foam. 

2.  If  only  a  small  amount  of  water  is  used  for  the  washing,  not 
enough  to  displace  all  the  potassium  hydroxide  solution,  the  column 
of  liquid  in  the  reservoir  and  its  connecting  tube  will  be  of  a  greater 
density  than  the  water  in  the  azotometer  tube.     This  means  that  the 
volume  of  nitrogen  will  be  somewhat  compressed  when  the  two 
columns  are  leveled  for  the  reading.     This  error  would  of  course 
aid  in  reducing  the  "normal"  error  which  is  always  too  much,  but 
any  known  error  in  manipulation  should  not  be  tolerated. 

3.  Some   azotometers  are  made   in   such  a  way  that  water  is 
retained  at  the  top  of  the  tube  under  the  stop-cock.     This  changes  the 
reading  of  the  volume  of  nitrogen.     By  gently  tapping  the  tube  it 
can  be  made  to  run  down  the  walls  to  the  liquid  below.     Then  allow 
it  to  stand,  etc. 

In  order  to  have  the  tube  ready  for  another  combustion, 
the  cupric  oxide  which  has  been  partially  reduced  must  be 
reoxidized.  Do  not  allow  the  cupric  oxide  to  cool  with  air 
in  the  tube  if  another  combustion  is  to  be  made.1  Without 
allowing  the  furnace  to  cool,  disconnect  the  azotometer, 
remove  the  reduced  copper  spiral  from  the  end  near  the 
azotometer,  and  while  the  tube  is  continued  to  be  heated  to 
redness  draw  air  through  it  for  several  minutes.  Then 
without  diminishing  the  heat  remove  the  remaining  air  and 
flood  the  apparatus  with  carbon  dioxide  in  the  usual  manner. 
Now  it  may  be  used  again  at  once,  or  it  can  be  closed  off 
and  the  cupric  oxide  allowed  to  cool  in  the  atmosphere  of 
carbon  dioxide  (p.  291). 

1  If  there  is  not  time  to  re-oxidize  the  cupric  oxide,  be  sure  to  let  the  tube 
cool  with  carbon  dioxide  in  it. 


300 


LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 


GENERAL  NOTES 

1.  Some  substances  give  off  gases,  such  as  methane,  which  are 
not  oxidized  by  the  cupric  oxide  in  the  absence  of  oxygen  gas.     These 
must  be  mixed  with  coarsely  powdered  lead  chromate  or  freshly 
precipitated  cuprous  chloride,  and  the  long  layer  of  cupric  oxide 
replaced  with  lead  chromate. 

2.  In  some  cases  the  entire  space  occupied  by  the  boat  must  be 
filled  with  cupric  oxide  mixed  with  the  substance  in  order  to  get 
intimate  contact. 

3.  If  any  nitric  oxide,  NO,  has  escaped  the  action  of  the  reduced 
copper  spiral  its  presence  can  be  shown  by  the  brown  fumes  formed 
when  the  nitrogen  gas  is  allowed  to  come  out  into  the  air.    Nitrogen 
as  nitric  oxide  occupies  only  half  the  volume  of  the  same  amount  of 
nitrogen  in  the  free  state. 

VIII.  Calculations,  and  Discussion  of  Results 

Having  ascertained  the  volume  of  the  nitrogen,  V,  its  tem- 
perature, /,  and  the  barometric  reading  and  the  temperature  of 
the  barometer  (p.  298),  correct  the  barometric  reading  to  zero 
by  using  the  following  formula  and  table.1 


where 


H0  =  corrected  reading  ; 
h  =  observed  reading; 
a  =  coefficient; 
/  =  temperature; 


h 

a 

h 

a 

h 

a 

h 

a 

720 

.1170 

736 

.1196 

752 

.1221 

768 

.1248 

722 

."73 

738 

.1199 

754 

.1224 

770 

.1251 

724 

.1176 

740 

.1202 

756 

.1228 

772 

.1254 

726 

.1180 

742 

.1205 

758 

.1231 

774 

•1257 

728 

.1183 

744 

.1208 

760 

•1235 

776 

.  1261 

730 

.1186 

746 

.1212 

762 

.1238 

778 

.1264 

732 

.1189 

748 

.1215 

764 

.1241 

780 

.1267 

734 

.1192 

750 

.1218 

766 

1245 

1  This  table  gives  the  correction  for  a  brass  scale.  The  correction  is  approx- 
imately 8  per  cent  greater  for  a  glass  scale.  It  is  very  convenient  to  place  a 
copy  of  this  table  for  ready  reference  in  the  case  surrounding  the  barometer, 


ORGANIC  COMBUSTIONS  301 

The  weight  of  the  nitrogen  can  now  be  found  by  the  formula: 

Wt.  in  grams  =  o.ooi 2507  X  V X  (g°~^  X  (  *73   . ; 

where  0.0012507  is  the  weight  of  i  cc.  of  pure  dry  nitrogen  at 
normal  temperature  and  pressure; 

V  =  volume  of  nitrogen  in  cubic  centimeters; 
HQ  =  corrected  barometric  pressure; 
p  =  vapor  pressure  of  water  at  f\ 
t  =  temperature. 

TABLE  OF  VAPOR  PRESSURE  OF  WATER  * 


f° 

mm. 

t 

mm. 

t° 

mm. 

t° 

mm. 

o 

4.6 

9 

8.6 

18 

15-5 

27 

26.7 

I 

4-9 

10 

9-2 

19 

16.5 

28 

28.4 

2 

5-3 

ii 

9.8 

20 

i7-5 

29 

30.1 

3 

5-7 

12 

io-5 

21 

18.7 

30 

31-8 

4 

6.1 

13 

II  .2 

22 

19.8 

31 

33-7 

5 

6-5 

14 

12.  O 

23 

21.  I 

32 

35-7 

6 

7.0 

15 

12.8 

24 

22.4 

33 

37-7 

7 

.   7-5 

16 

13-6 

25 

23-8 

34 

39-9 

8 

8.0 

17 

14-5 

26 

25.2 

35 

42.2 

The  weight  of  nitrogen  can  more  readily  be  obtained  by 
using  the  accompanying  tables  (page  303),  which  give  the 
weight  of  i  cc.  of  moist  nitrogen  at  different  temperatures  and 
pressures. 

The  percentage  of  nitrogen  in  the  substance  will  be: 

Per  cent  N==Wt  nitrogen  Xioo* 
Wt.  substance 

For  logarithmic2  calculation: 

1  From   Scheel  and  Heuse,  Ann.  Physik.,  31  (1910),  731,  as  given  in  the 
Smithsonian   Physical  Tables,  Third   Reprint  of  Sixth  Revised  Edition  (1918), 
154-5- 

2  A  table  of  four-place  logarithms  is  given  on  p.  308. 


302         LABORATORY  MANUAL  OF  ORGANIC  CHEMISTRY 

A  j,  f  Log.  wt.  i  cc.  N  at  t°  and  H0  = 

Ada          <  _ 

I  Log.  V 


f  Log.  wt.  total  nitrogen 

i 

[  Log.  100 


Subtract  , 

Log.  wt.  substance 

Log.  per  cent  N  = 

The  Limit  of  Error. — This  may  be  calculated  in  the  same 
general  way  as  given  on  p.  258.  For  results  of  analysis,  obtained 
by  the  method  described,  the  "  allowed  "  error  should  ordinarily 
not  be  more  than  10  parts  per  thousand,  and  never  more  than  20 
parts  per  thousand.  Check  results  should  also  come  within  these 
figures. 

The  following  results  are  given  as  being  typical  of  the  possibili- 
ties in  the  method:  ^-nitro-toluene  (CyHyC^N)  was  analyzed 
for  nitrogen  by  Mr.  S.  L.  Handforth  with  the  following  results 
(only  two  analyses  made) :  N  =  10.29%',  10.30%;  theory  calls 
for  N  =  10.22%.  The  error  here  is  6.9  and  7.8  parts  per  thousand, 
respectively.  The  same  substance  was  also  analyzed  by  Miss 
Sophia  Schulman,  N  =  10.09%,  10.23%,  10.18%;  error,  12.7 
(low),  0.9  and  3.9  (low)  parts  per  thousand;  and  also  by  Mr. 
H.  R.  Pyne,  N  =  10.15%,  IO-36%;  error,  6.8  (low),  13.7  parts  per 
thousand.  Mr.  T.  C.  Taylor  obtained  for  nitrogen  in  diphenyl- 
amine  (Ci2HnN),  N  =  8.28%,  8.32%;  theory,  N-8.28%;  one 
result  is  quite  fortuitous,  the  error  in  the  other  is  4.8  parts 
per  thousand.  Mr.  Geo.  H.  Walden  obtained  for  acetanilide 
(C8H9ON);  N=T- 10.3 2%,  10.43%;  theory,  N  =  10.37%;  error  is 
4.8  (low),  and  5.8  parts  per  thousand.  The  greatest  differ- 
ence in  the  results  in  any  of  .the  sets  of  determinations  men- 
tioned is  0.21  (Mr.  Pyne),  and  the  error,  based  on  the  lower 
figure,  is  20.7  parts  per  thousand. 


WEIGHT  OF  ONE  CUBIC  CENTIMETER  OF  MOIST         303 
NITROGEN  IN  MILLIGRAMS* 


t 

6692 

694 

696 

698 

700 

702 

704 

706 

708 

710mm 

5° 

1.108 

i  .  in 

1.114 

1.117 

I  .121 

1.124 

1.127 

1.130 

1-134 

I-I37 

04439 

04565 

04691 

04817 

04943 

05068 

05192 

05317 

05441 

05564 

6° 

i  .  103 

1.106  1.109 

1.113 

i  .  116 

i  .  119 

I  .  122 

i  .  125 

1.129 

1.132 

04251 

04378 

04504 

04630 

04755 

04880 

05005 

05130 

05254 

05378 

7 

1.098 

I  .  IOI 

i  .  105 

1.108 

i.  in 

i  .  114 

I.II7 

I  .  121 

1.124 

1.127 

04063 

04190 

04316 

04442 

04568 

04693 

04818 

04943 

05067 

05191 

8° 

1.093 

1.097 

I.  100 

1.103 

i  .106 

1.109 

I  .113 

I.II6 

1.119 

1.  122 

03877 

04003 

04130 

04256 

04382 

04507 

04632 

04757 

04881 

05005 

9° 

1.089 

1.092 

1  .095 

1.098 

I  .  IOI 

1.105 

I.IOS 

I  .  Ill 

i  .114 

I.II7 

03691 

03818 

03944 

04070 

04196 

04322 

04447 

04571 

04696 

04820 

10° 

1.084 

1.087 

1.090 

1.093 

1.097 

I.  100 

I  .  IO3 

I.I06 

i  .109 

I.II3 

03499 

03626 

03752 

03879 

04005 

04130 

04255 

04380 

04505 

04629 

11° 

1.079 

1.082 

1.085 

i.  088 

1.092 

1.095 

1.098 

I.  IOI 

1.104 

I.I07 

03300 

03427 

03554 

03680 

03806 

03932 

04057 

04182 

04307 

04431 

12° 

1.074 

1.077 

1.081 

1.084 

1.087 

1.090 

1.093 

1.096 

1.099 

I.I03 

03109 

03236 

03363 

03490 

03616 

03741 

03867 

03992 

04117 

04241 

13° 

1.069 

1.073 

i  .076 

1.079 

1.082 

1.085 

1.088 

I  .091 

1-095 

1.098 

02912 

03040 

03167 

03293 

03420 

03546 

03671 

03796 

03921 

04046 

14° 

i  .064 

1.068 

1.071 

1.074 

1.077 

1.080 

1.083 

I.  086 

1.089 

1.093 

02709 

02837 

02964 

03091 

03217 

03343 

03469 

03594 

03719 

03844 

15° 

1.059 

1.063 

1.066 

i  .069 

1.072 

1-075 

1.078 

I.OSl 

1.084 

1.088 

02507 

02635 

02762 

02889 

03016 

03142 

03268 

03393 

03518 

03643 

16° 

1-055 

1.058 

i  .061 

i  .064 

i  .067 

1.070 

1.073 

1.076 

1.079 

1.083 

02305 

02433 

02560 

02687 

02814 

02940 

03066 

03192 

03317 

03442 

17° 

1.050 

1-053 

1.056 

1-059 

1.062 

1  .065 

1.068 

I.O7I 

1.074 

1.077 

02097 

02225 

02353 

02480 

02607 

02734 

02860 

02985 

03111 

03236 

18° 

1-045 

i  .048 

1.051 

1-054 

1-057 

1.  060 

1.063 

1.066 

1.069 

1.072 

01890 

02018 

02146 

02273 

02400 

02527 

02653 

02779 

02905 

03030 

19° 

1.039 

i  .042 

1.046 

1.049 

1.052 

1-055 

1.058 

I  .O6l 

1.064 

1.067 

01676 

01805 

01933 

02060 

02188 

02314 

02441 

02567 

02693 

028l8 

20° 

1-034 

1.037 

i  .040 

1-043 

1.046 

1.049 

1-053 

1.056 

1.059 

I.O62 

oi457 

01585 

01713 

01841 

01969 

02096 

02222 

02349 

02475 

O26OO 

21° 

1.029 

1.032 

1-035 

1.038 

1.041 

1.044 

1.047 

1.050 

1-053 

I  .056 

01238 

01367 

oi495 

01623 

01751 

01878 

02005 

02I3I 

02257 

02383 

22° 

i  .024 

i  .027 

1.030 

1-033 

1.036 

1.039 

1.042 

1-045 

1.048 

I.05I 

01019 

01148 

01276 

01405 

01532 

01660 

01787 

01914 

02040 

O2l66 

23° 

1.018 

i  .021 

1.024 

i  .027 

1.030 

1.034 

1.037 

I  .040 

1-043 

I  .046 

00788 

00917 

01046 

01174 

01302 

01430 

01557 

01684 

01811 

01937 

24° 

1.013 

i  .016 

1.019 

i  .022 

i  .025 

1.028 

I.03I 

1.034  1.037 

I  .040 

00557 

00686 

00815 

00944 

01072 

OI2OO 

01328 

01455 

01582 

01708 

25° 

1.008 

I  .Oil 

1.014 

i  .017 

i  .020 

1.023 

1.026 

I  .029 

1.032 

1-035 

00326 

00456 

00585 

00714 

00843 

00971 

01099 

OI226 

oi353 

01480 

26° 

1.002   1.005 

1.008 

i  .on 

i  .014 

I.OI7 

I  .O2O 

1.023 

1.026 

I  .029 

OOO83  OO2I3 

00342 

00472 

00600 

00729 

.00857 

00985 

OIII2 

01239 

27° 

0.996  0.999 

i  .002 

1.005 

1.008 

i.  on 

I  .OI4 

I.OI7 

I  .O2O 

1.023 

99840  99970 

OOIOO 

00230 

00359 

00488 

OO6l6 

00744 

00872 

00999 

28° 

0.991   0.994 

0.997 

i  .000 

1.003 

i  .006 

I  .OO9 

1.  01  2 

I.OI5 

I.OlS 

995QO  99721 

99851 

99981 

OOIIO 

OO2  20 

00368 

00497 

00625 

00752 

29° 

0.985  0.988 

0.991 

0.994  0.997 

I  .OOO 

1.003 

I  .OO6 

I  .009 

I  .OI2 

99341  99472 

99603 

99733  99863 

99994 

OOI2I 

OO25O 

00378 

00506 

30° 

0.979  0.982 

0.985 

0.988!  0.991 

0-994 

0.997 

I  .OOO 

1.003 

I  .OO6 

99079  99211 

99341 

99472 

99602 

99732 

99861 

99990 

OOII9 

00247 

t 

6  692  694 

696 

698 

700 

702 

704 

706 

708 

710mm 

*From  the  Third  American    Edition    of  Gatterman's  "Practical   Methods  of  Organic, 
Chemistry,"  published  by  The  Macmillan  Company,  reprinted  by  permission. 


304         WEIGHT  OF  ONE    CUBIC  CENTIMETER  OF  MOIST 
NITROGEN  IN  MILLIGRAMS 


t 

6712 

714 

716 

718 

720 

722 

724 

726 

728 

730mm 

5° 

1.140 

i-i43 

1.146 

1.150 

1-153 

1.156 

i-i59 

1.163 

1.166 

i  .169 

05688 

05811 

05933 

06055 

06177 

06299 

06420 

06541 

06662 

06782 

6° 

i-i35 

1-138 

1.142 

1-145 

1.148 

1.151 

1-154 

1.158 

i  .  161 

i  .164 

05501 

05624 

05747 

05869 

05991 

06113 

06234 

06355 

06476 

06596 

7° 

1.130 

1-133 

1-137 

i  .  140 

1-143 

1.146 

1.149 

1-153 

i  .156 

I-I59 

05314 

05437 

05560 

05682 

05804 

05926 

06048 

06169 

06289 

06410 

8° 

1.125 

i  .129 

1.132 

i-i35 

1.138 

1.141 

1-145 

1.148 

1.151 

i-i54 

05128 

05251 

05374 

05497 

05619 

05741 

05862 

05983 

06104 

06225 

9° 

I  .121 

1.124 

1.127 

1.130 

1-133 

I-I37 

i  .140 

1-143 

i  .146 

1.149 

04943 

05067 

05190 

05312 

05434 

05556 

05678 

05796 

05920 

06041 

10° 

I  .Il6 

1.119 

I  .122 

1.125 

1.128 

1.132 

I-I35 

1.138 

i  .  141 

1.144 

04752 

04876 

04999 

05121 

05244 

05366 

05488 

05609 

05730 

05851 

11° 

I.  Ill 

1.114 

I.II7 

i  .  1  20 

1.123 

i  .  126 

1.130 

1-133 

1.136 

i-i39 

04555 

04679 

04802 

04925 

05047 

05169 

05291 

05412 

05534 

05654 

12° 

I  .IO6 

1.109 

I  .  112 

1.115 

1.118 

I  .122 

1.125 

1.128 

1.131 

1-134 

04365 

04489 

04612 

04735 

04857 

04980 

05101 

05223 

05344 

05465 

13° 

I.IOI 

1.104 

I.I07 

I.  1  10. 

1.113 

I.II7 

I  .  120 

1.123 

1.126 

i  .  129 

04170 

04293 

04417 

04540 

04662 

04785 

04907 

05029 

05150 

05271 

14° 

I  .096 

1.099 

I.IO2 

1.105 

1.108 

I  .  Ill 

I  .  114 

1.118 

I.  121 

1.124 

03968 

04092 

04215 

04339 

04461 

04584 

04706 

04828 

04949 

05070 

15° 

I  .091 

1.094 

1.097 

I  .  IOO 

1.103 

I  .IO6 

I  .  IO9 

1.113 

I  .Il6 

i  .  119 

03767 

03891 

04015 

04138 

04261 

04384 

04506 

04628 

04750 

04871 

16° 

1.086 

1.089 

I  .092 

1.095 

1.098 

I  .IOI 

I  .  IO4 

1.107 

I.  Ill 

1.114 

03567 

03691 

03815 

03938 

04061 

04184 

04306 

04428 

04550 

04672 

17° 

I.oSl 

1.084 

1.087 

1.090 

1.093 

I  .096 

1.099 

I  .  IO2 

I.I05 

1.108 

03361 

03485 

03609 

03733 

03856 

03979 

O4IOI 

04224 

04345 

04467 

18° 

1-075 

1.078 

1.082 

1.085 

i.  088 

I  .091 

1.094 

1.097 

I.  IOO 

1.103 

03155 

03279 

03403 

03527 

03650 

03774 

03896 

04019 

04141 

04262 

19° 

1.070 

1.073 

I  .076 

1.079 

1.082 

I.  086 

1.089 

1.092 

1-095 

1.098 

02943 

03068 

03192 

03316 

03440 

03563 

03686 

03808 

03931 

04053 

20° 

1.065 

i.  068 

I.O7I 

1.074 

1.077 

I.  080 

1.083 

I.  086 

1.089 

i  .092 

02725 

02850 

02975 

03099 

03223 

03346 

03469 

03592 

03715 

03837 

21° 

1.  060 

1.063 

1.066 

1.069 

1.072 

1-075 

1.078 

I.oSl 

1.084 

1.087 

02509 

02634 

02758 

02883 

03007 

03130 

03254 

03377 

03499 

03621 

22° 

1-054 

i-o57 

1.  060 

1.063 

1.066 

1.069 

1.073 

1.076 

1.079 

1.082 

02292 

02417 

02542 

02666 

02791 

02914 

03038 

03161 

03284 

03406 

23° 

1.049 

1.052 

1-055 

1.058 

1.061 

1.064 

1.067 

1.070 

1.073 

1.076 

02063 

02189 

02314 

02439 

02563 

02687 

028ll 

02934 

03057 

03180 

24° 

1-043 

1.046 

1.049 

1  .052 

1-055 

1.058 

I  .O6l 

I  .064 

1  .067 

1.070 

01834 

01960 

02085 

O22IO 

02335 

02459 

02583 

02707 

02830 

02953 

25° 

1.038 

1.041 

1.044 

1.047 

i  .050 

1-053 

1.056 

1-059 

1  .062 

1.065 

Ol6o6 

01732 

01858 

01983 

02108 

02233 

02357 

02481 

02604 

02727 

26° 

1.032 

1-035 

1.038 

I.04I 

1.044 

1.047 

1.050 

1-053 

1.056 

1-059 

01366 

01492 

Ol6l8 

01743 

01868 

01993 

O2Il8 

O2242 

02366 

02489 

27° 

I.O26 

i  .029 

1.032 

1-035 

1.038 

I  .041 

1.044   1.047 

1.050 

1-053 

OII26 

01252 

01378 

01504 

01630 

01755 

Ol879i  02OO4 

02128 

02251 

28° 

I  .O2O 

1.023 

I  .026 

I  .029 

1.032 

1.035   1.038 

I  .041 

1.044 

1.047 

00879 

01006 

OU33 

01259 

01384 

OI5IO 

01635 

o  759 

01884 

02008 

29° 

I.OI5 

i  .018 

I  .O2I 

1.024 

1.027 

1.030 

1-033 

1.036 

1.039 

i  .042 

00634 

00761 

00887 

OIOI4 

01140 

01265 

OI39I 

01516 

01640 

01764 

30° 

1.009 

i  .012 

I  .015 

1.018 

i  .021 

I  .024 

I  .027 

i  .029 

1.032 

1-035 

00375 

00502 

00629 

00756 

00882 

OIO08 

OH34 

01259 

01384 

01509 

t 

6712 

714 

716 

718 

720 

722 

724 

726 

728 

730mm 

WEIGHT  OF  ONE  CUBIC  CENTIMETER  OF  MOIST         303 
NITROGEN  IN  MILLIGRAMS 


t 

6732 

734 

736 

738 

740 

742 

744 

746 

748 

750mm 

5° 

1.172 

1.176 

1.179 

1.182 

1.185 

1.188 

1.192 

i-i95 

1.198 

I.2OI 

06902 

07021 

07141 

07259 

07378 

07496 

07614 

07732 

07849 

07966 

6° 

i  .167 

1.170 

1.174 

1.177 

1.180 

1.183 

1.187 

1.190 

1-193 

I.I96 

06716 

06835 

06955 

07074 

07192 

07311 

07429 

07546 

07664 

07781 

7° 

1.162 

1.166 

i  .169 

1.172 

I-I75 

1.178 

1.182 

1.185 

1.188 

I.I9I 

06530 

06650 

06769 

06888 

07007 

07125 

07243 

07361 

07479 

07596 

8° 

i-i57 

i  .161 

i  .  164 

1.167 

1.170 

i-i73 

1.177 

1.180 

1.183 

I.I86 

06345 

06465 

06584 

06703 

06822 

06941 

07059 

07177 

07294 

074II 

9° 

1.152 

i  .  156 

1.159 

1.162 

i  .165 

1.168 

1.172 

I-I75 

1.178 

I.lSl 

06161 

06281 

06400 

06520 

06638 

06757 

06875 

06993 

07111 

O7228 

10° 

1.147 

1.151 

1-154 

i-i57 

i  .  160 

i  .  163 

1.166 

1.170 

i  -173 

I.I76 

05971 

06091 

06210 

06330 

06449 

06567 

06686 

06804 

06922 

07039 

11° 

1.142 

I-I45 

1.149 

1.152 

I-I55 

1.158 

1.161 

i  .164 

1.168 

I.I7I 

05775 

05895 

06015 

06134 

06253 

06372 

06490 

06609 

06726 

06844 

12° 

i-i37 

i  .140 

1.144 

1.147 

i  .  150 

I-I53 

1.156 

I-i59 

1.163 

1.166 

05586 

05706 

05826 

05945 

06064 

06183 

06302 

06420 

06538 

06656 

13° 

1.132 

I-I35 

i-i39 

i  .  142 

I-I45 

1.148 

1.151 

I-I54 

I.I57 

1.161 

05392 

05512 

05632 

05751 

05871 

05990 

06108 

06227 

06345 

06463 

14° 

1.127 

1.130 

1-133 

1.136 

i  .  140 

1-143 

1.146 

i.i  9 

1.152 

I-I55 

05191 

05312 

05432 

05552 

05671 

05790 

05909 

06028 

06146 

06264 

15° 

I.  122 

1.125 

1.128 

1.131 

I-I34 

I-I37 

i  .  141 

1.144 

1.147 

1.150 

04992 

05H3 

05233 

05353 

05472 

05592 

05711 

05829 

05947 

06065 

16° 

I.  117 

I.  120 

1.123 

i  .126 

i  .129 

1.132 

I-I35 

1-138 

1.142 

1.  145 

04793 

04913 

05034 

05154 

05274 

05393 

05512 

05631 

05749 

05867 

17° 

I  .III 

I.II5 

1.118 

1.  121 

1.124 

1.127 

1.130 

I-I33 

1.136 

I-I39 

04588 

04709 

04830 

04950 

05070 

05189 

05308 

05427 

05546 

05664 

18° 

I  .IO6 

I  .IO9 

I  .112 

i  .  116 

i  .  119 

I  .  122 

1.125 

1.128 

1.131 

I.I34 

04384 

04505 

04625 

04746 

04866 

04986 

05105 

05224 

05343 

05461 

19° 

I  .IOI 

I  .  IO4 

I.  IO7 

r.no 

1.113 

I.II6 

1.119 

1.  122 

1.126 

1.129 

04174 

04295 

04416 

04537 

04657 

04777 

04896 

05015 

05134 

05253 

20° 

1-095 

1.099 

I.IO2 

1.105 

1.108 

I.  Ill 

i  .  114 

I.II7 

I.  I  20 

1.123 

03958 

04080 

O42OI 

04321 

04442 

04562 

04682 

04801 

O492O 

05039 

21° 

I  .090 

1.093 

I  .096 

1.099 

1.  102 

I.I05 

i  .108 

I.  Ill 

I.II5 

1.118 

03743 

03865 

03986 

04107 

04228 

04348 

04468 

04587 

04707 

04825 

22° 

1.085 

1.088 

I  .091 

1.094 

1.097 

I  .IOO 

i  .103 

1.106 

I.I09 

1.  112 

03528 

03650 

03772 

03893 

04013 

04134 

04254 

04374 

04493 

04612 

23° 

1.079 

1.082 

1.085 

1.088 

I  .091 

1.094 

1.097 

I.  IOO 

I.I03 

1.106 

03302 

03424 

03546 

03667 

03788 

03909 

04029 

04149 

04268 

04388 

24° 

1.073 

1.076 

I.OSO 

1.083 

1.086 

1.089 

1.092 

1.095 

1.098 

I.  IOI 

03076 

03198 

03320 

03441 

03562 

03683 

03804 

03924 

04044 

04163 

25° 

I.  068 

I.O7I 

1.074 

1.077 

1.080 

1.083 

1.086 

1.089 

I  .092 

1.095 

02850 

02972 

03094 

03216 

03338 

03459 

03579 

03700 

03820 

03940 

26° 

I.O62 

I  .065 

1.068 

i  .071 

1.074 

1.077 

1.080 

1.083 

1.086 

1.089 

O26l2 

02735 

02857 

02979 

03IOI 

03222 

03343 

03464 

03584 

03704 

27° 

I  .056 

*-059 

I  .062 

1.065 

1.068 

I.07I 

1.074 

1.077 

I.OSO 

1.083 

02375 

02498 

O262O 

02742 

02864 

02986 

03107 

03228 

03349 

03469 

28° 

1.050 

1-053 

1.056 

1-059 

1.062 

I  .065 

1.068 

1  .071 

1.074 

1.077 

02I3I 

02254 

02377 

02500 

O2622 

02744 

02865 

02986 

03107 

03228 

29° 

1.044 

1.047 

1.050 

1-053 

I  .056 

1.059 

i  .062 

1.065 

1.068 

1.071 

01888 

02012 

02135 

02258 

02380 

02502 

02624 

02745 

02867 

02987 

30° 

1.038 

I.O4I 

1.044 

1.047 

1.050 

1-053 

1.056 

1-059 

I  .062 

1.065 

01633 

01757 

01880 

02003 

O2I26 

02248 

02370 

02492 

O26l4 

02735 

t 

6732 

734 

736 

738 

740 

742 

744 

746 

748 

750mm 

306         WEIGHT  OF  ONE  CUBIC   CENTIMETER  OF  MOIST 
NITROGEN  IN  MILLIGRAMS 


t 

6752 

754 

756 

758 

760 

762 

764 

766 

768 

770mm 

6° 

i  .  205 

1.208 

I  .  211 

i  .  214 

i.  218 

I  .  221 

i.  224 

i  .  227 

i  .  230 

1.234 

08083 

08199 

08315 

08431 

08546 

08661 

08776 

08891 

09005 

09119 

6° 

1.199 

1.203 

I  .206 

1.209 

I  .  212 

I  .  2l6 

i  .  219 

I  .  222 

1.225 

1.228 

07898 

08014 

08130 

08246 

08361 

08477 

08592 

08706 

08820 

08934 

7° 

1.194 

1.198 

I  .  201 

i  .  204 

I  .  207 

I  .  210 

i  .  214 

I.2I7 

I  .  220 

1.223 

07712 

07829 

07945 

08061 

08177 

08292 

08407 

08522 

08636 

08750 

8° 

1.189 

i-i93 

I  .  196 

1.199 

I  .  2O2 

1.205 

1.208 

I  .  212 

I.2I5 

i.  218 

07528 

07645 

07761 

07877 

07993 

08108 

08223 

08338 

08452 

08566 

9° 

1.184 

1.188 

I  .  191 

1.194 

I.I97 

I  .200 

1.203 

I  .  207 

I  .  210 

1.213 

07345 

07462 

07578 

07694 

07810 

07925 

08040 

08155 

08270 

08384 

10° 

1.179 

1.182 

I.I86 

1.189 

I  .  192 

I-I95 

1.198 

I  .  201 

1.205 

1.208 

07156 

07273 

07389 

07505 

07621 

07737 

07852 

07967 

O8o8l 

08196 

11° 

1.174 

1.177 

I.lSo 

1.183 

I.I87 

I  .  190 

1-193 

I  .  196 

I.I99 

1.202 

06961 

07078 

07195 

07311 

07427 

07542 

07658 

07773 

07887 

08002 

12° 

1.169 

1.172 

I-I75 

1.178 

I.lSl 

I.I85 

1.188 

I  .  191 

I.I94 

I.I97 

06773 

06890 

07007 

07123 

07239 

07355 

07470 

07585 

07700 

07814 

13° 

i  .  164 

i  .167 

I  .  I7O 

1-173 

I  .  176 

I.I79 

1.182 

I.I86 

1.189 

I  .  192 

06580 

06697 

06814 

06930 

07046 

07162 

07278 

07393 

07508 

07622 

14° 

1.158 

1.161 

I.I65 

1.168 

I.I7I 

I.I74 

1.177 

I.lSo 

1.183 

1.187 

06381 

06498 

06615 

06732 

06848 

06964 

07080 

07195 

07310 

07425 

15° 

I-I53 

i  .156 

I-I59 

1.162 

I.I66 

I  .169 

1.172 

I-I75 

I.I78 

1.181 

06183 

06300 

06417 

06534 

06650 

06767 

06882 

06998 

07II3 

07228 

16° 

1.148 

1.151 

I-I54 

I-I57 

i  .  160 

I.I63 

1.166 

I  .  I7O 

I-I73 

i  .  176 

05985 

06103 

O6220 

06336 

06453 

06569 

06685 

06801 

06916 

07031 

17° 

i  .142 

1.146 

I.I49 

1.152 

I-I55 

I.I58 

1.161 

I  .  164 

I  .  167 

I  .  I/O 

05782 

05900 

06017 

06134 

06251 

06367 

06483 

06599 

06714 

06829 

18° 

I.I37 

1.140 

I-I43 

i  .  146 

1.149 

I-I53 

1.156 

I-I59 

I.I62 

1.165 

05579 

05697 

05814 

05931 

06048 

06165 

06281 

06397 

06512 

06627 

19° 

1.132 

I-I35 

I.I38 

i  .141 

1.144 

I.I47 

1.150 

I-I53 

I.I56 

I-I59 

05371 

05489 

05607 

05724 

05841 

05957 

06074 

06190 

06305 

06421 

20° 

1.126 

i  .129 

I.I32 

I-I35 

1.138 

I  .141 

I-I45 

I.I48 

I.I5I 

I.I54 

05157 

05275 

05393 

05510 

05627 

05744 

05861 

05977 

06093 

06208 

21° 

I  .121 

1.124 

I.I27 

1.130 

I-I33 

I.I36 

1-139 

I  .  142 

I-I45 

1.148 

04944 

05062 

05180 

05298 

?54i5 

05532 

05649 

05765 

05881 

05997 

22° 

I.II5 

1.118 

I  .  121 

i  .  124 

1.127 

I.I30 

i  •  i33 

1.136 

I-I39 

I.I43 

04731 

04849 

04967 

05085 

05203 

05320 

05437 

05553 

05669 

05785 

23° 

I  .IO9 

I  .  112 

I.II5 

i  .  119 

I  .  122 

I.I25 

1.128 

I.I3I 

I-I34 

I.I37 

04507 

04625 

04744 

04862 

04979 

05097 

05214 

05330 

05447 

05563 

24° 

I.I04 

I  .  IO7 

i  .  no 

1.113 

i  .  116 

I  .  119 

I  .  122 

I.I25 

I.I28 

1.131 

O4282 

O44OI 

04520 

04638 

04756 

04873 

04991 

05108 

05224 

05341 

25° 

1.098 

I  .101 

i  .  104 

1.107 

i  .  no 

I.II3 

i  .  116 

I  .  119 

I.  122 

1.125 

04059 

04178 

04297 

04415 

04533 

04651 

04769 

04886 

O5OO2 

05119 

26° 

I.O92 

1.095 

1.098 

I  .  101 

i  .  104 

I  .  IO7 

I  .  IIO 

I.II3 

I  .Il6 

i  .  119 

03823 

03943 

04062 

04180 

04299 

04417 

04534 

04652 

04769 

04886 

27° 

1.086 

1.089 

i  .092 

1-095 

1.098 

I  .  101 

1  .  104 

I  .  107 

I.  IIO 

1-113 

03589 

03708 

03828 

03946 

04065 

04183 

04301 

04419 

04536 

04653 

28° 

I.  080 

1.083 

i.  086 

1.089 

i  .092 

1.095 

1.098 

I  .  101 

I.IO4 

1.107 

03348 

03468 

03587 

03706 

03825 

03944 

04062 

04180 

04297 

04415 

29° 

1.074 

1.077 

i.  080 

1.083 

i.  086 

1.089 

1  .092 

1-095 

1.098 

I  .  IOI 

03108 

03228 

03348 

03467 

03586 

03705 

03823 

03941 

04059 

04177 

30° 

1.068 

I  .O7I 

1.074 

1.077 

1.080 

1.083 

1.  086 

1.089 

I  .092 

1.095 

02855 

02976 

03096 

03216 

03335 

03454 

03573 

03691 

03809 

03927 

t 

6752 

754 

756 

758 

760 

762 

764 

766 

768 

770mm 

WEIGHT  OF  ONE   CUBIC  CENTIMETER  OF  MOIST         3Q7 
NITROGEN  IN  MILLIGRAMS 


t 

6772 

774 

776 

778 

780mm 

5° 

1.237 

i  .  240 

1-243 

1.247 

i  .  250 

09233 

09346 

09459 

09572 

09684 

6° 

1.232 

1-235 

1.238 

1.241 

1-245 

09048 

09162 

09275 

09387 

09500 

7° 

i  .  226 

1.230 

1-233 

1.236 

1.239 

08864 

08977 

09090 

09203 

09316 

8° 

I.  221 

1.224 

1.228 

1.231 

1-234 

08680 

08794 

08907 

09020 

09133 

9° 

I  .  2l6 

1.219 

1.223 

i  .226 

i  .229 

08498 

08612 

08725 

08838 

08951 

10° 

I  .  211 

i  .214 

1.217 

i  .220 

i  .  224 

08310 

08423 

08537 

08650 

08763 

11° 

I  .2O6 

i  .  209 

I  .212 

1.215 

i.  218 

O8ll6 

08230 

08343 

08456 

08569 

12° 

I  .2OO 

1.203 

I  .207 

I  .  2IO 

1.213 

07929 

08043 

08156 

08269 

08383 

13° 

!-i95 

1.198 

I  .  2OI 

I  .204 

1.208 

07737 

07851 

07964 

08078 

08191 

14° 

1.190 

i-i93 

I  .196 

I.I99 

1.202 

07539 

07653 

07767 

07881 

07994 

15° 

1.184 

1.187 

I  .190 

I.I94 

I.I97 

07342 

07457 

07571 

07684 

07798 

16° 

1.179 

1.182 

1.185 

I.I88 

I  .191 

07146 

07260 

07374 

07488 

07601 

17° 

i  -173 

1.177 

I.lSo 

I.I83 

I.I86 

06944 

07058 

07173 

07287 

07400 

18° 

1.168 

1.171 

I.I74 

I.I77 

1.180 

06742 

06857 

06971 

07085 

07199 

19° 

1.162 

1.166 

I  .  169 

I.I72 

i-i75 

06536 

06651 

06765 

06879 

06993 

20° 

I.IS7 

i  .  160 

1.163 

I.I66 

i  .  169 

06324 

06439 

06553 

06668 

06782 

21° 

1.151 

I-I54 

I-IS7 

1.160 

1.163 

06112 

06227 

06342 

06457 

06571 

22° 

1.146 

1.149 

I.I52 

I-I55 

1.158 

05901 

06016 

06131 

06246 

06360 

23° 

1.140 

i-i43 

1.146 

1.149 

1.152 

05679 

05791 

05909 

06024 

06139 

24° 

i-i34 

I-I37 

I.I40 

1.  143 

1.146 

05457 

05572 

05688 

05803 

05917 

25° 

1.128 

1.131 

I-I34 

I-I37 

i  .  140 

05235 

05351 

05467 

05582 

05697 

26° 

I  .122 

1.125 

I.I28 

1.131 

I-I34 

05002 

05118 

05234 

05349 

05465 

27° 

1.116 

i  .119 

I.  122 

1.125 

1.128 

04770 

04886 

05OO2 

05118 

05233 

28° 

1.  110 

1.113 

i  .  116 

i  .  119 

1.  122 

04531 

04648 

04764 

04880 

04996 

29° 

1.104 

i  .  107 

i  .  no 

1.113 

i  .  116 

04294 

04411 

04527 

04644 

04759 

30° 

1.098 

I  .  101 

1.104 

i  .107 

I  .  IIO 

04045 

04162 

04278 

04395 

04511 

t 

6772 

774 

776 

778 

780mm 

308 


LOGARITHMS 


Natural 
Numbers. 

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

PROPORTIONAL  PARTS. 

1 

2 

3 

1 

5 

6 

7 

8 

9 

IO 

0000 

0043 

0086 

0128 

0170 

0212 

0253 

0294 

0334 

0374 

4 

8 

12 

17 

21 

35 

29 

33 

37 

II 

0414 

0453 

0492 

0531 

0569 

0607 

0645 

0682 

0719 

0755 

4 

8 

II 

15 

19 

*3 

26 

30 

34 

12 

0792 

0828 

0864 

0899 

0934 

0969 

1004 

1038 

1072 

1106 

3 

7 

10 

14 

17 

21 

24 

28 

31 

13 

1139 

H73 

1206 

1239 

1271 

1303 

1335 

1367 

1399 

1430 

3 

6 

10 

13 

16 

19 

23 

26 

29 

14 

1461 

1492 

1523 

1553 

1584 

1614 

1644 

1673 

1703 

1732 

3 

6 

9 

12 

15 

18 

21 

24 

27 

15 

1761 

1790 

1818 

1847 

1875 

1903 

1931 

1959 

1987 

2014 

3 

6 

8 

11 

4 

*7 

20 

22 

35 

16 

2041 

2068 

2095 

2122 

2148 

2175 

2201 

2227 

2253 

2279 

3 

5 

8 

II 

3 

1  6 

18 

ax 

34 

I? 

2304 

2330 

2355 

2380 

2405 

2430 

2455 

2480 

2504 

2529 

2 

5 

7 

IO 

2 

15 

17 

20 

22 

18 

2553 

2577 

2601 

2625 

2648 

2672 

2695 

2718 

2742 

2765 

2 

5 

7 

9 

2 

14 

16 

19 

21 

19 

2788 

2810 

2833 

2856 

2878 

2900 

2923 

2945 

2967 

2989 

2 

4 

^ 

9 

1 

13 

16 

18 

20 

20 

3010 

3032 

3054 

3075 

3096 

3"8 

3139 

3160 

3181 

3201 

2 

A 

6 

8 

I 

13 

^ 

17 

19 

21 

3222 

3243 

3263 

3284 

3304 

3324 

3345 

3365 

3385 

3404 

2 

4 

6 

8 

O 

12 

L 

1  6 

1  8 

22 

3424 

3444 

3464 

3483 

3502 

3522 

354i 

356o 

3579 

3598 

2 

4 

6 

8 

1 

12 

i 

IS 

17 

23 

3617 

3636 

3655 

3674 

3692 

37ii 

3729 

3747 

3766 

3784 

2 

4 

6 

7 

( 

II 

3 

IS 

17 

24 

3802 

3820 

3838 

3856 

3874 

3892 

3909 

3927 

3945 

3962 

2 

4 

C 

7 

( 

II 

It 

14 

1  6 

25 

3979 

3997 

4014 

4031 

4048 

4065 

4082 

4099 

4116 

4133 

2 

3 

7 

( 

10 

2 

14 

IS 

26 

4150 

4166 

4183 

4200 

4216 

4232 

4249 

4265 

4281 

4298 

2 

3 

7 

8 

10 

XX 

13 

15 

27 

4314 

4330 

4346 

4362 

4378 

4393 

4409 

4425 

4440 

4456 

2 

3 

6 

8 

9 

11 

13 

14 

28 

4472 

4487 

4502 

4518 

4533 

4548 

4564 

4579 

4594 

4609 

2 

3 

6 

8 

9 

II 

12 

14 

2Q 

4624 

4639 

4654 

4669 

4683 

4698 

4713 

4728 

4742 

4757 

1 

3 

6 

7 

9 

IO 

12 

13 

30 

4771 

4786 

4800 

4814 

4829 

4843 

4857 

4871 

4886 

4900 

I 

3 

6 

7 

9 

IO 

II 

13 

31 

4914 

4928 

4942 

4955 

4969 

4983 

4997 

5011 

5024 

5038 

I 

3 

6 

7 

8 

IO 

XI 

12 

32 

505i 

5065 

5079 

5092 

5105 

5H9 

5132 

5M5 

5159 

5172 

1 

3 

i 

7 

8 

J 

II 

12 

33 

5185 

5198 

5211 

5224 

5237 

5250 

5263 

5276 

5289 

5302 

I 

3 

5 

6 

8 

J 

10 

12 

34 

5315 

5328 

5340 

5353 

5366 

5378 

539i 

5403 

54i6 

5428 

I 

3 

4 

c 

6 

8 

9 

10 

II 

35 

5441 

5453 

5465 

5478 

5490 

5502 

5514 

5527 

5539 

555i 

I 

2 

4 

5 

6 

7 

9 

10 

II' 

36 

5563 

5575 

5587 

5599 

5611 

5623 

5635 

5647 

5658 

5670 

I 

2 

4 

5 

6 

7 

8 

IO  II 

37 

5682 

5694 

5705 

5717 

5729 

5740 

5752 

5763 

5775 

5786 

I 

2 

2 

5 

6 

7 

8 

9  10 

38 

5798 

5809 

5821 

5832 

5843 

5855 

5866 

5877 

5888 

5899 

I 

2 

3 

5 

6 

7 

8 

9|io 

39 

59" 

5922 

5933 

5944 

5955 

5966 

5977 

5988 

5999 

6010 

I 

a 

3 

4 

5 

7 

.8 

9 

10 

40 

6021 

6031 

6042 

6053 

6064 

6075 

6085 

6096 

6107 

6117 

I 

2 

3 

4 

6 

8 

9 

10 

4i 

6128 

6138 

6149 

6160 

6170 

6180 

6191 

6201 

6212 

6222 

I 

2 

3 

4 

c 

6 

7 

8 

9 

42 

6232 

6243 

6253 

6263 

6274 

6284 

6294 

6304 

6314 

6325 

I 

2 

3 

4 

e 

6 

7 

8 

9 

43 

6335 

6345 

6355 

6365 

6375 

6385 

6395 

6405 

6415 

6425 

I 

2 

3 

4 

c 

6 

7 

ft 

9 

44 

6435 

6444 

6454 

6464 

6474 

6484 

6493 

6503 

6513 

6522 

I 

2 

3 

4 

5 

6 

7 

8 

9 

45 

6532 

6542 

6551 

6561 

657i 

6580 

6590 

6599 

6609 

6618 

I 

2 

3 

4 

5 

6 

7 

8 

9 

46 

6628 

6637 

6646 

6656 

6665 

6675 

6684 

6693 

6702 

6712 

I 

2 

3 

4 

5 

6 

7 

7 

8 

47 

6721 

6730 

6739 

6749 

6758 

6767 

6776 

6785 

6794 

6803 

I 

2 

3 

4 

5 

5 

6 

7I  8 

48 

6812 

6821 

6830 

6839 

6848 

6857 

6866 

6875 

6884 

6893 

I 

2 

3 

4 

4 

5 

6 

7 

8 

49 

6902 

6911 

6920 

6928 

6937 

6946 

6955 

6964 

6972 

6981 

I 

2 

3 

4 

4 

S 

6 

7 

8 

50 

6990 

6998 

7007 

7016 

7024 

7033 

7042 

7050 

7059 

7067 

I 

2 

3 

3 

4 

5 

6 

7 

8 

5i 

7076 

7084 

7093 

7101 

7110 

7118 

7126 

7135 

7143 

7152 

I 

2 

3 

3 

4 

5 

6 

7 

,. 

52 

7160 

7168 

7177 

7185 

7193 

7202 

7210 

7218 

7226 

7235 

I 

2 

2 

3 

4 

5 

6 

7|  7 

53 

7243 

7251 

7259 

7267 

7275 

7284 

7292 

7300 

7308 

7316 

I 

2 

2 

3 

4 

5 

0 

6 

7 

54 

7324 

7332 

7340 

7348 

7356 

7364 

7372 

7380 

7388 

7396 

I 

2 

2 

3 

4 

a 

6 

6 

7 

LOGARITHMS 


309 


Natural 
Numbers. 

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

PROPORTIONAL  PARTS 

1 

2 

3 

1 

r> 

6 

7 

8 

55 

7404 

7412 

74i9 

7427 

7435 

7443 

745i 

7459 

7466 

7474 

2 

3 

4 

5 

5 

6 

56 

7482 

7490 

7497 

7505 

7513 

7520 

7528 

7536 

7543 

755i 

2 

3 

4 

5 

5 

6 

57 

7559 

7566 

7574 

7582 

7589 

7597 

7604 

7612 

7619 

7627 

2 

3 

4 

5 

5 

6 

58 

7634 

7642 

7649 

7657 

7664 

7672 

7679 

7686 

7694 

7701 

2 

3 

4 

4 

5 

6 

59 

7709 

7716 

7723 

773i 

7738 

7745 

7752 

7760 

7767 

7774 

2 

3 

4 

4 

5 

6 

60 

7782 

7789 

7796 

7803 

7810 

7818 

7825 

7832 

7839 

7846 

2 

3 

4 

4 

5 

6 

6l 

7853 

7860 

7868 

7875 

7882 

7889 

7896 

7903 

7910 

7917 

2 

3 

4 

4 

5 

6 

62 

7924 

793i 

7938 

7945 

7952 

7959 

7966 

7973 

798o 

7987 

2 

3 

3 

4 

5 

6 

63 

7993 

8000 

8007 

8014 

8021 

8028 

8035 

8041 

8048 

8055 

2 

3 

3 

4 

5 

5 

64 

8062 

8069 

8075 

8082 

8089 

8096 

8102 

8109 

8116 

8122 

2 

3 

3 

4 

5 

5 

65 

8129 

8136 

8142 

8149 

8156 

8162 

8169 

8176 

8182 

8189 

2 

3 

3 

4 

$ 

S 

66 

8i95 

8202 

8209 

8215 

8222 

8228 

8235 

8241 

8248 

8254 

2 

3 

3 

4 

s 

5 

67 

8261 

8267 

8274 

8280 

8287 

8293 

8299 

8306 

8312 

8319 

2 

3 

3 

4 

5 

S 

68 

8325 

833i 

8338 

8344 

835i 

8357 

8363 

8370 

8376 

8382 

2 

3 

3 

4 

4 

5 

69 

8388 

8395 

8401 

8407 

8414 

8420 

8426 

8432 

8439 

8445 

2 

2 

3 

4 

4 

5 

70 

8451 

8457 

8463 

8470 

8476 

8482 

8488 

8494 

8500 

8506 

2 

2 

3 

4 

4 

5 

7i 

8513 

8519 

8525 

853i 

8537 

8543 

8549 

8555 

8561 

8567 

2 

2 

3 

4 

4 

5 

72 

8573 

8579 

8585 

859i 

8597 

8603 

8609 

8615 

8621 

8627 

2 

2 

3 

4 

4 

5 

73 

8633 

8639 

8645 

8651 

8657 

8663 

8669 

8675 

8681 

8686 

2 

2 

3 

4 

4 

5 

74 

8692 

8698 

8704 

8710 

8716 

8722 

8727 

8733 

8739 

8745 

2 

2 

3 

4 

4 

5 

75 

875i 

8756 

8762 

8768 

8774 

8779 

8785 

8791 

8797 

8802 

2 

2 

3 

3 

41 

5 

76 

8808 

8814 

8820 

8825 

8831 

8837 

8842 

8848 

8854 

8859 

2 

2 

3 

3 

4 

5 

77 

8865 

8871 

8876 

8882 

8887 

8893 

8899 

8904 

8910 

8915 

2 

3 

3 

4 

4 

78 

8921 

8927 

8932 

8938 

8943 

8949 

8954 

8960 

8965 

8971 

2 

3 

3 

4 

4 

79 

8976 

8982 

8987 

8993 

8998 

9004 

9009 

9015 

9020 

9025 

2 

3 

3 

4 

4 

80 

9031 

9036 

9042 

9047 

9053 

9058 

9063 

9069 

9074 

9079 

2 

3 

3 

4 

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247 

268 

5290 

?3H 

4 

6 

3 

5 

7 

19 

•97 

333 

354 

376 

397 

P4I9 

441 

462 

484 

5506 

?528 

4 

7 

9 

3 

5 

7 

20 

.98 

550 

572 

594 

616 

?638 

66  1 

683 

705 

5727 

9750 

4 

7 

9 

3 

6 

8 

zo 

•99 

772 

795 

817 

840 

?863 

886 

908 

93i 

?954 

?977 

5 

7 

9 

4 

6 

8 

20 

312  LIST  OF  APPARATUS  FOR  GENERAL  ORGANIC  CHEMISTRY 

LIST    OF    APPARATUS    FOR    GENERAL    ORGANIC 
CHEMISTRY  L 

Box  I — ARTICLES  RETURNABLE 

Cat.  No.  2 

i  Addition  tube Emil  Greiner 

i  Adapter  tube E.  &  A.     no 

i  Beaker,  lipped,  Griffin's  low  form,  50  cc E.  &  A.     737 

I  Beaker,  lipped,  Griffin's  low  form,  100  cc E.  &  A.     737 

i  Beaker,  lipped,  Griffin's  low  form,  150  cc E.  &  A.     737 

i  Beaker,  lipped  (Pyrex),  Griffin's  low  form,     250  cc E.  &  A.     737 

i  Beaker,  lipped,  Griffin's  low  form,  400  cc E.  &  A.     737 

i  Beaker,  lipped,  Griffin's  low  form,  600  cc E.  &  A.     737 

i  Beaker,  lipped,  Griffin's  low  form,  800  cc E.  &  A.     737 

1  Beaker,  lipped,  Griffin's  low  form,  1000  cc E.  &  A.     737 

6  Bottles,  sq.,  G.  S.,  for  handing  in  liquid  preparations,  15  cc E.  &  A.     926 

6  Bottles,  wide-mouthed,  glass-stoppered,  round,  10  cc.,  for  handing 

in  solid  preparations E.  &  A.     934 

2  Bottles,  tincture,  narrow  mouth,  G.  S.,  250  cc E.  &  A.     918 

3  Bottles,  wide  mouth,  250  cc E.  &  A.     910 

Calcium  chloride  tube,  6-inch E.  &  A.   7052 

Condenser,  sealed  joints,  bulbed  inner  tube,  12  inches  long E.  &  A.   2246 

Condenser,  straight  inner  tube E.  &  A.   2243 

Condenser,  inner  tube,  "air  condenser,"  i5-inch E.  &  A.  2240 

Watch  glass,  3-inch  (cover  glass) E.  &  A.  7382 

Watch  glass,  4^-inch  (cover  glass) E.  &  A.   7382 

Bottle,  sealing  tube,  15  cc 

Cylinder,  graduated,  100  cc E.  &  A.   2512 

Cylinder,  graduated,    10  cc E.  &  A.   2512 

Evaporating  dish,  pore.,  6  cm.  diam.  (Coors) E.  &  A.     501 

2  Flasks,  distilling,  round  bottom,  30  cc.  (Pyrex) E.  &  A.  3065 

2  Flasks,  distilling,  B.  &  C.,  round  bottom,    50  cc.  (Pyrex) E.  &  A.  3065 

2  Flasks,  distilling,  B.  &  C.,  round  bottom,  125  cc.  (Pyrex) E.  &  A.  3065 

1  Flask,  distilling,  B.   &  C.,  round  bottom,  250  cc.  (Pyrex) E.  &  A.  3065 

2  Flasks,  Erlenmeyer,  150  cc E.  &  A.  3027 

2  Flasks,  Erlenmeyer,    50  cc E.  &  A.  3027 

i  Flask,    Erlenmeyer,  250  cc E.  &  A.  3027 

Flask,  heavy  glass,  for  filtering,  with  side  neck,  500  cc E.  &  A.  3090 

Glass  evapora ting-dish,  5  cm E.  &  A.  2624 

Flask,  round  bottom,      1 25  cc E.  &  A.  3050 

Flask,  round  bottom,       250  cc E.  &  A.  3050 

Flask,  round  bottom,      300  cc.,  short  neck E.  &  A.  3057 

Flask,  round  bottom,      500  cc E.  &  A.  3050 

Flask,  round  bottom,     1000  cc E.  &  A.  3050 

Funnel,  4  cm.  diam E.  &  A.  3216 

1  See  preface,  p.  v. 

2  These  are  given  for  the  sake  of  convenience  only. 


LIST  OF  APPARATUS  FOR  GENERAL  ORGANIC  CHEMISTRY  313 

Cat.  No. 

i  Funnel,  7.5  cm.  diam.,  short  stem,  special E.  &  A.  3216 

i  Funnel,  dropping,  60  cc E.  &  A.  3302 

i  Funnel,  separatory,  Squibb's,  250  cc E.  &  A.  3300 

i  Funnel,  Buchner,  porcelain,  5  cm.  diam.   (Coors) E.  &  A.  630 

i  Gooch  perforated  plate 

i  Set  of  three  thermometers,  short  scale,  with  case  (Fisher) E.  &  A. 

1  Thermometer,  milk  glass  scale,  360°  C E.  &  A.  6746 

6  Test-tubes,  4"X£" . .  E.  &  A.  7210 

12  Test-tubes,  6"Xf" E.  &  A.  7216 

3  Test-tubes,  8"X i". .............. '.'. E.  &  A  .  7216 

2  Test-tubes,  side  neck,  6"Xi". E.  &  A.  7218 

i  Melting-point  apparatus 

i  Hard  glass  test-tube,  Pyrex,  special,  10  cm.Xg  mm 

i  Mortar,  glass  lipped,  2f  inches E.  &  A.  4616 

i  Pestle  for  above,  glass '. E.  &  A.  4616 

i  Spatula  and  spoon  combined,  pore.,  12  cm Coors,  553 

1  Glass  stop-cock,  2  mm E.  &  A.  6468 

Box  II —  ARTICLES   RETURNABLE 

Cat.  No. 

2  Burette  clamps,  iron E.  &  A.  2006 

2  Burners,  Tirrilh : . .  .    E.  &  A.  1462 

i  Burner  chimney. E.  &  A.  1586 

1  Burner,  star  support  for  chimney. -. . . . . E.  &  A.  1608 

2  Condenser  clamps,  iron,  large E.  &  A.  2020 

2  Condenser  clamps,  iron,  medium E.  &  A.  2016 

4  Clamp  holders,  for  j^-inch  rods E.  &  A.  2044 

i  Set  of  rings  for  steam-bath 

i  Filter  pump  with  special  Columbia  coupling  medium,  4!  inches..   E.  &  A.  5624 

1  Oil  bath,  iron,  6-inch,  modified E.  &  A.  616 

2  Ring  stands,  medium,  iron,  modified  in  shop E.  &  A.  6540 

i  Ring  for  iron  stand,  2  inches . . . . E.  &  A.  6010 

i  Ring  for  iron  stand,  3  inches E.  &  A.  6010 

i  Set  cork  borers,  Nos.  1-9  brass  (Old  Cat.) E.  &  A.  2841 

i  Screw  clamp E.  &  A.  2080 

i  Test-tube  rack,  copper . 

i  Tripod,  4^  inches  diam E.  &  A.  7000 

i  Wing  top  for  burner E.  &  A.  1616 

1  Set  weights,  rental  .75  (Columbia  Style  B) 

The  following  pieces  of  apparatus  are  too  large  to  go  into  the  packing  box, 
but  the  student  will  need  them  immediately,  therefore  he  should  go  to  the 
Stockroom  and  draw  them  at  once  on  a  new  debit  card. 

2  Ring  stands,  large,  iron,  extra  heavy,  modified  in  shop E.  &  A.  6040 

The  following  and  other  apparatus  may  be  obtained  at  the  Stockroom  at  any 

time  as  needed: 

Manometer  stand  Porcelain  casseroles 

Hot-water  funnel  Evaporating  dishes 


314  LIST  OF  APPARATUS  FOR  GENERAL  ORGANIC  CHEMISTRY 

Funnels,  Nos.  5  and  6  (i  2  cm.  and  1 5  cm.)     Special  distilling-flasks 
Electric  motor  Instruments 

Stirring  apparatus  Glass  stop-cocks 

Desiccators  Large  condensers,  bulbed  or  straight  inner 

Wind  shields  tubes 

Etc. 

Box  II— ARTICLES  NON-RETURNABLE 

Cat.  No. 
4  Lengths  glass  tubing,  6  mm.  bore,  2^  ft E.  &  A.  3730 

2  Lengths  glass  rod,  4  mm.  bore,  2^  ft E.  &  A.  3726 

3  Porous  tiles 

File,  rat  tail,  5  inches E.  &  A.  2864 

File,  rat  tail,  7  inches .' E.  &  A.  2864 

File  triangular,  5  inches E.  &  A.  2866 

Wire  gauze,  4  inches  square E.  &  A.  7450 

Steel  spatula,  7.5  cm E.  &  A.  6272 

Sodium  knife  (common  knife) E.  &  A.  2300 

Test-tube  brush,  sponge  end E.  &  A.  1 210 

Test-tube  cleaner E.  &  A.  1214 

Package  filter  paper,  12^  cm.,  Whatman  No.  2 E.  &  A.  5001 

Boxes  matches 

Test-tube  holder,  nickel E.  &  A.  2068 

Sponge E.  &  A.  6378 

Box  labels,  square E.  &  A. 

2  Towels 

8  Feet  black  rubber  tubing,  ^  inch  I.  D E.  &  A.  6054 

12  Feet  white  rubber  tubing,  I  inch  I.  D.,  heavy  walled E.  &  A.  6048 

1  Pair  goggles,  wire  gauze  protectors E.  &  A.  3794 

2  Dozen  assorted  corks,  sizes  1-15 l E.  &  A.  2284 

Suberite  ring,  2§  inches  I.  D E.  &  A.  6020 

Cake  Pummo  soap 

Tin  pail 

Locks  with  keys,  Eagle  Lock  Co 

Vial  litmus  paper,  neutral,  Squibb's 

Pocket  ruler 

Rubber  stopper  No.  7,  3  holes,  to  fit  25o-cc.  bottle E.  &  A.  6040 

Rubber  stopper  No.  5,  i  hole,  to  fit  test-tube,  with  side  neck E.  &  A.  6040 

Rubber  stopper,  3  holes  to  fit  25o-cc.  short  neck  R.  B.  flask.  ...    E.  &  A.  6040 
Rubber  stopper,  No.  5,  2  holes  to  fit  test-tube  with  side  neck. .  .   E.  &  A.  6040 

Scissors E.  &  A.  6104 

Cork  screw,  Williamson  Wire  Novelty  Co g£ 

Rubber  washer 

Perfection  sand  paper  holder H.  &  S.    1017 

Package  sand  paper,  4i"X4i"  1 

1  For  keeping  Alberene  desk  top  clean. 


LIST  OF  CHEMICALS  FOR  LONG  COURSE 


315 


LIST  OF  CHEMICALS  FOR  LONG  COURSE1 

FIRST  SEMESTER 


Reagent 
No. 

Name  and  Specification. 

Amount. 

Kind  of 
Container. 

I 

Acetone 

30  cc 

G.  S  B  2 

2 

Acetophenone                  .      .... 

10  gms. 

G.  S.  B. 

•} 

Alcohol  95%                      . 

2X300  cc.3 

G.  S.  B. 

4' 

Amyl  alcohol  (iso)           

«           I  CC. 

G.  S.  B. 

5 
6 

Aniline  from  sulfate  for  B.  P.  determination 
Anisic  .acid,  powdered,  for  M.  P.  determi- 
nation            .             

15  cc. 
o.  i  gm. 

G.  S.  B. 

Vial 

7 

Anthracene,  powdered,  for  M.  P.  determi- 
nation    

o.  i  gm. 

Vial 

8 

Anthraquinone,  powderrd,  for  M.  P.  deter- 
mination                                                  . 

o  i  gm. 

Vial 

Benzine   70—80°             .... 

I<?  CC. 

G.  S.  B. 

10 

Benzoic  acid                                       .... 

i  gm. 

Vial 

ii 

Benzoic  acid,  powdered,  for  M.  P.  determi- 
nation 

o  .  i  gm. 

Vial 

12 

Bromine 

I  OZ. 

G.  S.  B. 

I  3 

Bromine  water                  .  .    

2<C  CC. 

G.  S.  B. 

14 

T  r 

Bromine,  5%  in  carbon  tetrachloride  
Calcium  chloride  anhyd    gran     . 

20  cc. 
100  gms. 

G.  S.  B. 
C.  S.  B.2 

16 

Calcium  carbide  lumps 

15  gms. 

C.  Vial 

17 

Calcium  oxide                                        .    .  • 

150  gms. 

WM.,  G.  S.  B.2 

18 

Carbazol,  powdered,  for  M.  P.  determina- 
tion                                  

o.i  gm. 

Vial 

TO 

Chloroform 

10  cc. 

G.  S.  B. 

*v 

20 

Copper  oxide  powder       

2  gms. 

Vial 

21 

Copper  sulfate  anhyd        

•>  gms. 

C.  Vial 

Copper  sulfate  crystals                        .  . 

i  gm. 

Vial 

22 

Copper  sulfate  -BTJ-  molar.       

3  cc. 

C.  S.  B. 

24. 

Copper  turnings                         

5  gms. 

Vial 

Copper  wire 

2ft. 

Vial 

ZO 
26 

Cotton  absorbent                  

2  gms. 

Vial 

1  See  preface,  p.  v. 

2  Abbreviations:    G.  S.  B.  =  glass   stoppered   bottle;    C.  S.  B.  =  cork   stoppered   bottle; 
WM.  =  wide-mouthed. 

3  The  amounts  of  such  reagents  as  alcohol,  ether,  sulfuric  acid  are  only  nominal.     These 
must  be  added  to  later  in  the  work. 


316 


LIST  OF  CHEMICALS  FOR  LONG  COURSE 


LIST  OF  CHEMICALS  FOR  LONG    COURSE— Continued 
FIRST  SEMESTER 


Reagent 
No. 

Name  and  Specification. 

Amount. 

Kind  of 
Container. 

27 
28 

Di-nitrobenzoic  acid  (1:3:5)  
Ether,  Merck's  

i  gm. 
2X5  Ib. 

Vial 
Cans 

20 

Ethyl  bromide 

2C  CC 

C  S  B 

3O 

Fehling's  solution  A  1  

C.  CC. 

G.  S.  B. 

31 

Fehling's  solution  B 

tr  CC. 

G  S  B 

32 

Formalin  

2<  CC. 

G.  S.  B. 

22 

Glass  wool  

20  cc. 

Vial 

2,4 

Glycerol 

IO  CC. 

C  S  B 

2C 

Hydrochloric  acid,  cone  

35  cc- 

G.  S.  B. 

36 

Hydroxylamine  hydrochloride 

1  .  c.  gms. 

WM.,  G.  S.  B. 

77 

Iodine   ... 

17  ems. 

WM.  G.  S  B 

3.8 

Lime  water 

IO  CC 

C  S  B 

7Q 

Magnesium  (Grignard's)  

<\  ems. 

Vial 

4O 

Menthol      

e  ems. 

C.  Vial 

41 

Methylal  

2  CC. 

S.  T.2 

42 

Methyl  alcohol  

2  CC. 

C.  S.  B. 

43 

Naphthalene,  powder,  for  M.  P.  determi- 
nation 

o  i  gm 

Vial 

44 

Phenolphthalein,  sol  

c,  cc. 

C.  S.  B. 

45 

Phosphoric  acid  (1.7)  

40  cc. 

G.  S.  B. 

46 

Phosphorus  pentachloride 

i  gm 

S.  T. 

47 

Phosphorus,  red.  

2  gms. 

Vial 

48 

Pinene  

IS  CC. 

C.  S.  B. 

40 

Porous  tile  gran 

10  gms. 

Vial 

CO 

Potassium  carbonate,  fused,  

15  gms. 

C.  Vial 

ci 

Potassium  hydroxide  .     .  .       

^  ems. 

C.  Vial 

52 

C2 

Potassium  hydroxide,  purified  by  alcohol  .  . 
Potassium  permanganate  

3  gms. 
2  gms. 

C.  Vial 
Vial 

54 

Quinoline  (synthetic)  for  B.  P.  determina- 
tion    ,.  ,  ,.  ,  .  .  t  

15  cc. 

G.  S.  B. 

cc 

Rapeseed  oil  ,  ,  t  ,  ,,,,..,... 

300  cc. 

C.  S.  B. 

56 

2  CC. 

C.  S.  B. 

57 

Salicylic  acid,  powder,  for  M.  P,  determi- 
nation    ,...,.,,,,... 

o.i  gm. 

Vial 

58 

Schiff's  aldehyde  reagent  (fuchsine  sulfur- 
ous  acid)  

IO  CC. 

G.  S.  B. 

•JO 

Soda  lime,  dry  

20  cc. 

C.  Vial 

60 

Sodium  bicarbonate            

«c  gms. 

Vial. 

1  The  ground  part  of  the  glass  stopper  of  the  bottle  containing  the  "alkaline  half"  of 
Fehling's  solution  is  dipped  in  melted  paraffin  before  being  used.  This  prevents  the  stopper 
from  becoming  "frozen."  Cork  and  rubber  stoppers  cannot  be  used. 

2S.  T.  =  sealed  tube. 


LIST  OF  CHEMICALS  FOR  LONG  COURSE 


317 


LIST  OF  CHEMICALS  FOR  LONG  COURSE— Continued 
FIRST  SEMESTER 


Reagent 
No. 

Name  and  Specification. 

Amount. 

Kind  of 
Container. 

fir 

Vial 

fi? 

r  s  TC 

62 

Sodium  carbonate  dry 

CL. 

Vial 

uo 
6d 

Sodium  chloride,  sat.  sol.  .  »v,v.v.v.v.".v 

0  61113' 

<o  cc. 

C.  S.  B. 

fie 

C  Vial 

uo 
66 

Sodium  metallic                

1  2  gms 

WM    G.  S  B 

67 

Sulfuric  acid  cone                «*.' 

300  cc. 

(in  can) 
G.  S.  B. 

68 

Sulfuric  acid,  fuming  

I^  CC. 

S.  T. 

60 

Vaseline                                     .-..•.-.•.... 

IO  CC. 

Vial 

7O 

Zinc  dust                                

10  gms. 

Vial 

318 


LIST  OF  CHEMICALS  FOR  LONG  COURSE 


LIST  OF  CHEMICALS  FOR  LONG  COURSE1 
SECOND  SEMESTER 


Reagent 
No. 

Name  and  Specification. 

Amount. 

Kind  of 
Container. 

I 

Acetic  acid  (glacial)  

7C  CC 

G.  S  B  l 

2 

Acetic  anhydride         

12  CC 

G  S  B 

Acetylacetone 

I  CC 

G  S  B 

Acetacetic  ester  

I  CC 

G  S  B 

Acetone 

2  ?  CC 

C  S  B 

6 

Alcohol,  95%  

2X300  cc.1 

C  S  B 

7 

Aluminium  chloride  (anhyd.) 

52ms 

C  Vial 

8 

Ammonium  acetate  (dry)  

iq  gms. 

C  Vial 

Ammonium  hydroxide,  cone  

qo  cc 

G  S  B 

10 

ii 

Ammonium  molybdate  reagent  
Aniline  I  

25  cc. 
<  cc. 

G.  S.  B. 
G.  S  B 

12 

Animal  charcoal  

e  ems. 

Vial 

17 

Anthracene 

2  ^  cms 

Vial 

14 

Benzene,  8o°-82°  

115  cc. 

C.  S.  B 

iq 

Benzene,  thiophene  free           .       .... 

7,    CC. 

G  S  B 

16 

Benzaldehyde 

"\  CC 

C  S  B 

17 

Benzyl  chloride  

IS  CC. 

S.  tube 

18 

Bleaching  powder.  .  .  . 

e  ems. 

C  vial 

10 

Bromine 

I  OZ 

G  S  B 

20 

Bromine  water  

IO  CC. 

G.  S.  B. 

21 

Bromine  in  CC14,  5%  

I  CC. 

G  S  B. 

22 

Butter 

10  gms 

27 

Cane  sugar 

5  grins.. 

Vial 

24 

Carbon  disulfide  

I  CC. 

C  S  B 

2C 

Catechol 

o  i  gm 

Vial 

26 

Chloroform  U  S  P 

20  cc 

C  S  B 

27 

Chromium  trioxide   .          

4  t;  gms. 

C.  vial 

28 

Cinnamic  acid 

o  i  gm 

Vial 

2O 

Copper  carbonate  (basic) 

o  *»  gm 

Vial 

3O 

Copper  sulfate  N                

7  cc. 

C.  S.  B. 

7.1 

Corn  cob  (ground) 

i  gm. 

Vial 

72 

Cotton  (absorbent) 

o  *i  cm 

Vial 

77 

Dimethylaniline                    

2  CC. 

G.  S.  B. 

7,4 

Dimethyl  sulfate                              

30  gms. 

S.  tube 

7T 

Diphenyl-thiourea                                     .  • 

o  01  gm. 

Vial 

16 

Egg 

i 

Shell 

77 

Ether  (Merck's)              

2X5  Ib.1 

Cans 

38 

Ether  ("over  sodium")      

oo  cc. 

C.  S.  B. 

7Q 

Ethyl  ammonium  chloride  .       

2  CC. 

C.  S.  B. 

1  See  foot-notes,  p.  315. 


LIST  OF  CHEMICALS  FOR  LONG  COURSE 


319 


LIST  OF  CHEMICALS   FOR  LONG  COURSE— Continued 
SECOND  SEMESTER 


Reagent 
No. 

Name  and  Specification. 

Amount. 

Kind  of 
Container. 

Ethyl  bromide 

2O  CC 

C  S  B 

4.1 

Fehling's  solution  "  A"  

31?  CC. 

G.  S.  B.1 

A  2 

Fehling's  solution  '  '  B  "  

3^  CC. 

G.  S.  B. 

Ferric  chloride  >-  molar 

<  CC 

C  S  B 

4,5 

44 

AC 

Ferric  chloride,  N  
Ferrous  sulfate                      .  .  . 

2  CC. 

i  em. 

C.  S.  B. 
Vial 

4.6 

Ferrous  sulfide  

20  gms. 

Vial 

47 

Gallic  acid                  

o  01  gm. 

Vial 

A& 

Gelatine 

i  gm. 

Envelope 

AT\ 

Gum  arabic        

o.  <;  gm. 

Vial 

CQ 

Hydrochloric  acid  cone 

125  cc. 

G  S  B 

y* 

ej 

Hippuric  acid  

i  gm. 

Vial 

r  2 

Iron  powder                            

<;  inns. 

Vial 

Iron  nails  (small) 

3  ems. 

Vial 

30 

CA 

Lactose               

12  gms. 

Vial 

ce 

Lead  acetate  N                                         .  . 

10  cc. 

C  S  B 

$6 

Magnesium  sulfate,  cryst  

6  gms. 

Vial 

r  7 

Methyl  iodide                            .  .        

I  CC. 

S  tube 

<8 

Michler's  ketone 

o  i  gm. 

Vial 

59 
60 

Monomethyl  aniline,  commercial  
Nitric  acid  cone 

I  CC. 

60  cc. 

G.  S.  B. 
G  S  B 

61 

Nitric  acid  fuming 

I  CC. 

S  tube 

62 

Nitrobenzene,  commercial  

20  cc. 

C  S  B 

<n 

Phenol 

13  2ms. 

Vial 

6/1 

Phthalic  anhydride 

o  2  grn. 

Vial 

65 
66 

Phenylhydrazine  
Phosphorus  oxy  chloride.. 

2  CC. 
2  CC. 

G.  S.  B. 
S  tube 

67 

Phosphorus  trichloride  

5  cc. 

S.  tube 

68 

Potassium  carbonate  (fused)   

2<  cms. 

C  vial 

60 

Potassium  cyanate 

O    ^  £. 

Vial 

7o 

Potassium  fluoride  

0.5  g. 

Vial 

71 

Potassium  iodide  N/io 

2  CC. 

C  S  B 

72 

Potassium  permanganate 

10  gms. 

Vial 

77 

Potassium  ethyl  sulfate  

o  .  5  gm  . 

Vial 

74. 

Pyridine  commercial             ... 

e  cc. 

G  S.  B 

7  ? 

Quinoline 

2  CC 

G  S  B 

76 

Resorcinol  

o.  i  gm. 

Vial 

77 

Salicylic  acid                          ....        .... 

o  i  gm. 

Vial 

78 

Schiff  '  s  aldehyde  reagent 

20  cc 

Amb  G   S  B 

1  See  foot-note,  p.  316. 


320 


LIST  OF  CHEMICALS  FOR  LONG  COURSE 


LIST  OF  CHEMICALS  FOR   LONG  COURSE— Continued 
SECOND  SEMESTER 


Reagent 
No. 


Name  and  Specification. 


Amount. 


Kind  of 
Container. 


79  Silver  nitrate,  N/io. 10  cc. 

80  Sodium,  metallic 12  gms. 

81  Sodium  bisulfite,  sat.  sol 10  cc. 

82  Sodium  carbonate,  cryst 4  gms. 

83  Sodium  chloride,  commercial 4  Ibs. 

84  Sodium  chloride,  sat.  sol 50  cc. 

85  Sodium  dichromate 15  gms. 

86  Sodium  hydroxide 50  gms. 

87  Sodium  nitrite 8  gms. 

88  Sodium  nitroprusside o .  i  gm. 

89  Starch,  soluble 5  gms. 

90  Sulfanilic  acid i  gm. 

91  Sulfuric  acid  (fuming) 6  cc. 

92  Tannin  (tannic  acid) 2  gms. 

93  Tin,  granulated 35  gms. 

94  Toluene,  commercial no  cc. 

95  Toluidine  (ortho) 5  cc. 

96  Triphenyl-chlor-methane 0.5  gm. 

97  Xylene,  commercial 30  cc. 

98  Zinc  chloride,  N 10  cc. 

99  Zinc  dust,  commercial 5  gms. 

100  Zinc,  powdered i  gm. 


Amb.  G.  S.  B. 

WM.,  G.  S.  B. 

(in  can) 

C.  S.  B. 

Vial 

Bag 
C.  S.  B. 
C.  vial 
C.  vial 

Vial 

Vial 

Vial 

Vial 
S.  tube 

Vial 

Vial 
C.  S.  B. 
G.  S.  B. 

Vial 
C.  S.  B. 
C.  S.  B. 

Vial 

Vial 


LIST  OF  CHEMICALS  FOR  SHORT  COURSE 
LIST  OF  CHEMICALS  FOR  SHORT  COURSE1 


321 


Reagent 
No. 

Name  and  Specification. 

Amount. 

Kind  of 
Container. 

I 

Acetic  acid  glacial        

IOO  CC 

G  S  B  l 

2 

Acetic  anhydride 

I  3   CC 

GSR 

2 

Acetacetic  ester  

M  «-«-• 
I  CC 

G  S  B 

Acetylacetone        

I  CC 

G  S  B 

Acetone 

2  C.  CC 

C  S  B  l 

6 

Alcohol,  95%       

2  X3OO  CC  * 

G  S  B 

Ammonium  acetate 

i  ^  firms 

C  vial 

8 

Ammonium  hydroxide,  cone  

e,o  CC. 

G  S  B 

Ammonium  molybdate,  sol 

2  C  CC 

G  S  B 

10 

Amyl  alcohol  (iso)  

I  CC. 

G.  S.  B 

ii 

Aniline  I  

Is?  CC. 

G  S  B 

12 

Aniline  from  sulfate,  for  B.  P.  determina- 
tion    „  

15  CC. 

G.  S  B 

I? 

Animal  charcoal.  .  .         

i  ^  firms 

Vial 

14 

Anthracene,  powdered,  for  M.  P.  determi- 
nation   

o  i  gm. 

Vial 

If 

Benzene,  8o°-82°        .... 

I  5  CC 

C  S  B 

16 

Benzene  (thiophene  free)  

3  CC. 

C.  S.  B. 

17 

Benzine  7o°-8o°  

ic  CC 

G  S  B 

18 

Benzaldehyde 

Sec 

C  S  B 

IQ 

Benzoic  acid  

i  gm. 

Vial 

2O 

Bleaching  powder  . 

5  firms 

Vial 

21 

Bromine 

5CC 

G  S  B 

22 

Bromine  water  

2<  CC 

G  S  B 

23 
24 

Bromine,  5%  in  carbon  tetrachloride  
Butter  

2O  CC. 

10  gms. 

G.  S.  B. 

2C. 

Calcium  chloride,  anhydrous,  gran  

2c  ems 

C.  S  B 

26 

Calcium  carbide  lumps     

i<  firms 

Vial 

27 

Calcium  oxide 

150  gms 

WM    C  S  B 

28 

Cane  sugar  

e  gms. 

Vial 

2O 

Catechol 

o  ?  cm. 

Vial 

3O 

Chloroform  

fJO  CC. 

G.  S.  B. 

21 

Cinnamic  acid                         

o  i  gm. 

Vial 

22 

Copper  carbonate  basic 

o  ^  firm. 

Vial 

22 

Copoer  oxide  powder 

5  firms 

Vial 

24 

Copper  sulfate  anhyd      

c,  ems. 

C.  vial 

2C 

Copper  sulfate  cryst 

i  gm. 

Vial 

26 

Copper  sulfate,  N  sol   

5  cc. 

C.  S.  B. 

27 

Copper  turnings            .       

<  gms. 

Vial 

38 

Copper  wire  No  16 

2  ft. 

Vial 

2Q 

Cotton,  absorbent  

2  gms. 

Vial 

i  See  preface,  p;  v.  and  also  foot-notes,  p.  315. 


322  LIST  OF  CHEMICALS  FOR  SHORT  COURSE 

LIST  OF  CHEMICALS  FOR  SHORT  COURSE— Continued 


Reagent 
No. 

Name  and  Specification. 

Amount. 

Kind  of 
Container. 

4° 

Dimethyl  aniline  

2  CC. 

G.  S.  B. 

41 

Diphenyl-thiourea 

o  01  gm 

Vial 

42 

Egg  

i 

Shell 

41 

Ether  (Merck's)  

2X5  lb. 

Cans 

44 

AK 

Ethyl  ammonium  chloride,  sol  
Ethylene  dibromide 

2  CC. 
2  CC 

C.  S.  B. 
C  S  B 

46 

Fehling's  solution,  "A"  l  

2O  CC. 

G.  S.  B. 

47 

Fehling's  solution,  "B"  

20  cc. 

G  S  B 

48 

Ferric  chloride,  -^  molar 

20  cc 

C  S  B 

40 

Ferrous  sulfate 

i  crm 

Vial 

CO 

Ferrous  sulfide  

20  gms. 

Vial 

ci 

Gallic  acid  

o  i  gm 

Vial 

52 

Glass  wool  

20  cc. 

Vial 

S3 

Hippuric  acid  

i  gm. 

Vial 

54 

Hydrochloric  acid,  cone 

150  cc 

G  S  B 

55 

Hydroxylamine  hydrochloride  

i  .  <  cms. 

WM.  G.  S.  B. 

<;6 

Iodine  resublimed 

17  crms 

WM    G  S  B 

«57 

Iron  powder  

c  gms. 

Vial 

58 

Lead  acetate,  N  sol  

10  cc 

C  S  B 

CO 

Lime  water 

IO  CC 

C  S  B 

60 

Methyl  iodide  

I  CC. 

SealT 

61 

Michler's  ketone  

o  i  gm 

Vial 

62 

Monomethyl  aniline 

I  CC 

C  S  B 

63 

Naphthalene,  powdered,  for  M.  P.  deter- 
mination   

o  i  gm 

Vial 

64 

Nitric  acid,  cone 

CQ    CC 

G  S  B 

6e 

Nitric  acid  fuming 

I  CC 

Seal  T 

66 

Nitrobenzene,  commercial  

20  cc 

C  S  B 

67 
68 

Nitrobenzene,  for  B.  P.  determination.  .  . 
Phthalic  anhydride 

15  cc. 

o  2  gms 

C.  S.  B. 

Vial 

60 

Phenolphthalein  sol 

e  rp 

C  S  B 

70 

Phenylhydrazine  .  .  .        .    . 

e  CC 

G  S  B 

71 

Phosphorus  red 

2  cms 

Vial 

72 

Phosphorus  pentoxide  

4  gms. 

C.  vial 

7? 

Phosphorus  oxychloride  

2  CC 

SealT 

74 

Phosphorus  trichloride 

71  CC 

Seal  T 

7c 

Pinene 

1  1  CC 

C  S  B 

76 

77 

Porous  tile,  small  broken  pieces  
Potassium  carbonate,  anhyd  

20  CC. 

20  gms. 

C.  vial 
C   vial 

78 

Potassium  hydroxide  

Sgms 

C   vial 

79 

Potassium  hydroxide,  purified  by  alcohol  . 

3  gms. 

C.  vial 

1  See  foot-note,  p.  316. 


LIST  OF  CHEMICALS  FOR  SHORT  COURSE  323 

LIST  OF  CHEMICALS  FOR  SHORT~COURSE— Continued 


Reagent 
No. 

Name  and  Specification. 

Amount. 

Kind  of 
Container. 

go 

Potassium  flouride      

o.c  cm 

Vial 

81 

2  CC. 

C.  S.  B 

82 

Potassium  permanganate  

tj  gms 

Vial 

8* 

Pyridine  commercial 

e  CC 

G  S  B 

84 

Quinoline  

2  CC. 

G.  S  B. 

8< 

Rapeseed  oil     ....       

300  cc 

C  S  B 

86 

o  .  2  gm. 

Vial 

8? 

Salicylic  acid  

o  i  gm. 

Vial 

88 
80 

Salicylic  acid,  for  M.  P.  determination  .  . 

O.I 

20 

Vial 
Amb.  G.  S.  B. 

GO 

Silver  nitrate  sol    N/io  

2C  CC. 

Amb.  G  S  B 

OI 

I"\  CC. 

C.  S.  B. 

O2 

Sodium  dichromate,  commercial  

20  gms. 

C.  vial 

O3 

Sodium  chloride  sat  sol 

50  cc 

C  S  B 

Od. 

Sodium  chloride  

100  gms. 

C.  S.  B. 

O? 

Sodium  carbonate  cryst 

10  gms 

Vial 

06 

Sodium  hydroxide  

2%  gms. 

C.  vial 

O7 

Sodium  nitrite               

8  gms. 

Vial 

Q8 

o.oi  gm. 

Vial 

OQ 

Starch  soluble  

r  gms. 

Vial 

IOO 

Sulfanilic  acid 

i  gm 

Vial 

IOI 

Sulfuric  acid,  cone  

IOO      CC. 

G.  S.  B. 

IO2 

Sulfuric  acid  fuming 

10  cc 

SealT 

IO3 

3^  gms. 

Vial 

I  O4. 

Toluidine  (ortho)  

IT   CC. 

G.  S.  B. 

IO"\ 

Vaseline                                     .    ... 

10  cc. 

Vial 

106 

10  cc. 

C.  S.  B. 

IO7 

Zinc  dust,  commercial  

10  gms. 

Vial 

GENERAL   INDEX 


NOTE. — Substances   with  a   prefix  such  as   /-menthone,  ^-tolunitrile,  etc.,  are 
indexed  under  the  name  of  the  substance  regardless  of  the  prefix. 


Absorption  bottles,  how  to  fill,  for 
water  ........................ 

Absorption  bottles,  how  to  fill,  for 
CO2  .......................... 

Absorption  bottles,  weighing  ..... 

—  train  ....................... 

Accident,  in  case  of  .............. 

Acetacetic     ester,     ferric    chloride 

test  .......................... 

Acetaldehyde,     preparation    from 
aldehyde  ammonia  ...... 

—  ,  —  of  a  solution  of  ........... 

—  ammonia,  preparation  of  ....... 

Acetals  ........................ 

Acetamide,  preparation  of  ........ 

—  sealed  tube  method  ........... 

0-Acetamino-benzoic  acid,  prepara- 

tion of  ....................... 

Acetanilide,  formation  of 
Acetanthranilic  acid,  preparation  of 
Acetic  acid,  for  accidents  ......... 

Acetone,  chemical  properties  of  ____ 

—  for  drying  apparatus  ........... 

Acetophenone,  reduction  of  ....... 

Acet-o-toluidide,  preparation  of  .  .  . 
Acetylacetone,  ferric  chloride  test.  . 
Acetylation,  with  acetic  anhydride  . 

—  ,  —  acetyl  chloride  .......  IO3~4> 

Acetyl  chloride,  preparation  of.  ... 

--  reactions  .................. 

Acetylene,  from  calcium  carbide.  .  . 

—  ,  —  ethylene  dibromide  ........ 

—  ,  properties  of  ................. 

Acetylides,  cuprous  .............. 

—  ,  silver  ....................... 

Acids,  accidents  ................. 


240 

243 

248 

236 

6 

178 

90 

83 

85 

94 

115 

117 


189 
6 

98 

15 

73 

164 

178 

164 

J65 

102 

103 

50 

52 

50 

51 

50 

6 


Addition  tube 13 

Alcohol,  absolute,  preparation  of . .     26 

—  boiling-point 24 

—  for  drying  apparatus 15 

—  fractionation  of  mixture 22 

— ,  secondary,  preparation  of 73 

— ,  tertiary,  preparation  of 69 

Alcoholic  potash,  for  halogen  test. .     38 

Alcohols,  identification  of 55 

— ,  reactions  of 54 

Aldehyde  ammonia,  see  Acetalde- 
hyde ammonia. 

Aldehydes,  tests  for 91 

Alkalies,  accidents 6 

Alkylation  of  an  hydroxyl  group. . .   180 

Alumina,  preparation  of 238 

Aluminium    chloride,    in    Friedel- 

Crafts'  reaction 144 

,  opening  sealed  bottles  of ...   144 

—  mercury  couple,  reference  for.. .   146 

—  oxide,  preparation  of 238 

Amino  acid,  preparation  and  prop- 
erties    124 

acetic  acid,  preparation  of ....   1 24 

Amylene,  in    tests    for    ''double 

bond." 45 

Aniline,  preparation  of 157 

Animal   charcoal   for   decolorizing 

Solutions 125,  150,  164,  167 

Anisole,  preparation  of 180 

Anthraquinone,  preparation  of. ...   210 
Atomic  weights,  table  of. 

Inside  back  cover. 

Autoxidation  of  benzaldehyde 182 

Azotometer,  for  nitrogen  combus- 
tion     285 

— ,  testing 287 


325 


326 


GENERAL  INDEX 


B 

Babo  funnel 159 

Barometer,  table  of  corrections  for.  300 

Baths  for  heating,  metal 79 

,  oil 79 

Bending  glass  tubing 28 

Benzaldehyde,  reactions 182 

Benzene,  chemical  properties 138 

— ,  historical  note 139 

—  sulfonic   acid,   sodium   salt,   prepa- 
ration of 152 

Benzidine  rearrangement 169 

Benzine,  properties 32 

Benzolene,  name  for  benzine 33 

Benzyl  chloride,  in  Friedel- Crafts' 

reaction 144 

,  test  for  halogen  in 150 

Blank  determinations,  method  of 

running 246 

Blankets,  for  fire 6 

Boat,  for  organic  combustions ....   236 

—  tube  ("  piggie  ") 251 

Boiling,  discussion  of .  . 1.7 

Boiling-point,  correct 17, 18 

— ,  correction    for    change    in    air 

pressure. 16 

Boiling-point,  definition 17 

— ,  determination  of 7 

— ,  liquids  for  determining 17 

Bomb-tube,  how  to  seal 117 

Boric  acid  for  accidents 6 

Brombenzene,  preparation  of 149 

Bromination  of  an  aromatic  hydro- 
carbon    149 

Bromine,  accidents 6 

— ,  bottles,  method  of  opening ....     33 

Bubble  counter 227 

Bumping,  causes  and    methods    of 

prevention 19 

Butter,  hydrolysis  of 108 


Calcium     chloride    for    absorbing 
water  in  organic  combustions ...   239 
—  for  drying  liquids,  see  Dry- 
ing agents. 

Calcium  chloride  tube,  filling 27 


Calculations   for  carbon  and  hy- 
drogen   257 

— ,  for  nitrogen 300 

Camphene,  preparation  of 202 

Camphor,  preparation  of 208 

Cane  sugar,  hydrolysis  of 127 

Carbon,  determination  of 217 

— ,  tests  for 30 

Carbon  dioxide  generator  for  nitro- 
gen combustion 275 

Carron  oil  for  accidents 6 

Castor  oil  for  alkali  in  the  eye ....  6 

Catechol,  ferric  chloride  test 178 

Cellulose  acetate,  formation  of. ...  137 

Cerium  dioxide,  preparation  of. ...  234 

Chemicals,  amounts 3 

— ,  lists,  see  List  of  chemicals. 

— ,  weighing 3 

Chromic  acid,  oxidation  with. 54,  83,  85 

99,  210 

Cinnamic  acid,  decomposition 183 

,  reduction  to  hydrocinnamic 

acid 184 

Claisen  distilling  flask 76 

Combustion  of  gases 268 

explosive  substances 269 

—  —  liquids 267 

substances   containing   mer- 
cury   267 

Combustion  of  substances  contain- 
ing nitrogen 265 

Combustion  of  substances  contain- 
ing phosphorus 267 

Combustion  of  substances  contain- 
ing sodium 267 

Combustion  of  substances  contain- 
ing sulfur 266 

Combustion  proper,  for  carbon  and 

hydrogen 253 

Combustion  proper,  for  nitrogen . .  293 

—  tube,  for  the    determination   of 

carbon  and  hydrogen 231 

Combustion  tube,  for  nitrogen. ...  284 

Condenser,  air 15 

— ,  bulbed 26 

— ,  Liebig 13 

— ,  reflux 26 

— ,  water 10, 13 


GENERAL  INDEX 


327 


Copper     oxide,     gauge,     roll     of, 

("  spiral  ") 228,  235 

Copper  oxide,  in  qualitative  test  for 

carbon 30 

Copper  oxide,  preparation  of,  for 

nitrogen  combustion 288 

Copper  sulfate,  in  test  for  water  in 

alcohol 26 

Corks,  boring 10 

Crystal  violet,  formation  of 171 

,  preparation  of 175 

Cuprous  chloride  solution,  ammo- 

niacal 50 

Cuprous  cyanide,  for  Sandmeyer 

reaction 187 

D 

Decolorization  with  animal  char- 
coal  125,  150,  164,  167 

Desiccator,  vacuum 87 

Diazotization 170,  177,  187 

p  Dibrombenzene,  formation  of 150 

trans-i  .8-Dichlor-terpane,  prepara- 
tion of 195 

Dimethylaniline,    hi    test   for   3°- 

amine 165 

Dimethyl-ethyl-carbinol,    prepara- 
tion of 69 

Dimethyl    sulfate,    as    alkylating 

agent 180 

Dinitro-benzene,  formation  of 139 

3.5-Dinitrobenzoic  acid,  for  identi- 
fication of  alcohols 55 

Diphenylmethane,  preparation  of . .  144 
Diphenylsulfone,  formation  of.i38,  152 
Diphenylthiourea,  in  test  for  ele- 
ments   112 

Discussion  of  results,  for  carbon  and 

hydrogen 258 

Discussion  of  results,  for  nitrogen.  301 

Distillation,  apparatus  for 10 

— ,  fractional 22 

—  in  vacua 76 

—  with  steam 158 

Distilling  flasks,  Claisen 76 

,  Ladenburg n,  22 

,  ordinary n 

Double  bond,  tests  for.  .44, 48, 183, 185 


Drying  agents  for  liquids,  anhy- 
drous sodium  sul- 
fate  177,191 

,  calcium  chloride ...  37, 154 

,  fused    potassium  car- 
bonate  71,  74 

,  solid  sodium  hydroxide  160 

Drying  pieces  of  apparatus 15 

Dumas  method  for  nitrogen 269 

Dyes,  azo,  methyl  orange 170 

— ,  triphenylmethane,  crystal  vio- 
let  i7iji7S 

Dyes,    triphenylmethane,    phenol- 

phihalein 171 

Dyes,    triphenylmethane,    fluores- 
cein 171 


Electric  combustion  furnace.. . .  230,  283 

Empirical  formula 260 

Emulsions,  "  breaking,"  foot-note .     36 
Error,  limit  of,  for  carbon  and  hy- 
drogen   258 

Error,  limit  of,  for  nitrogen 301 

Errors  in  combustions,  and  how  to 

avoid  them 261 

Ester,  formation  of  an,  by  addition 

of  an  acid  to  an  olefine 205 

Ester,  formation  of  an,  by  replace- 
ment of  a  metal  in  a  salt 122 

Ester,  formation  of  an,  from  an 

acid  chloride  and  an  alcohol.  .55,  104 
Ester,  formation  of  an,  from  an  al- 
cohol and  an  acid 54,  106, 191 

Ester,  formation  of  an,  from  an 

alcohol  and  an  acid  anhydride. .   137 
Ester,  hydrolysis  of  an. . .  106,  108,  206 

— ,  ortho  (reference) 94 

Esterification,   by  addition  of  an 

acid  to  an  olefine 205 

Esterification,  by  means  of  the  alco- 
hol and  acid 106, 191 

Ethene,  see  Ethylene. 

Ether  for  drying  apparatus 15 

— ,  distillation  of 70, 161 

— ,  drying 69 

—  extraction 74 

Ethyl  acetate,  hydrolysis  of 106 


328 


GENERAL  INDEX 


Ethyl  acetate,  preparation  of 106 

Ethylamine  hydrochloride,  in  test.    121 
Ethyl  ammonium  chloride,  in  test  121 

Ethylbenzene,  preparation  of 141 

Ethylene,  chemical  properties. .  .  44,   48 
— ,  preparation  from  alcohol  and 

phosphoric  acid 40 

Ethylene,  preparation  from  alcohol 

and  phosphorus  pentoxide 48 

Ethylene  dibromide,  preparation  of    40 

,  properties  of 45 

Ethyl  iodide,  preparation  of 35 

,  properties 38 

—  isocyanate,  formation  and  prop- 
erties  . . . 122 

Extraction  with  ether 74 

Eye,  alkali  in 6 


Fehling's    solution,    reduction  of, 

with  aldehydes 91, 182 

Fehling's  solution,  reduction  of, 

with  sugars 127 

Filter,  fluted 128 

— ,  hardened 170 

Fire,  in  case  of 6 

—  extinguisher 6 

Fittig's  synthesis  of  an  aromatic 

hydrocarbon 141 

Flasks,  Claisen 76 

— ,  distilling 1 1 

— ,  Erlenmeyer 13,14 

— ,  Ladenburg 11,22 

Fluorescein,  formation  of 171 

Fluted  filter 128 

Formaldehyde  reactions 96 

— ,  resorcinol  test 96 

Fractionation  apparatus  or  column  25 

Friedel-Crafts'  reaction 144 

Fuchsine-sulfurous  acid  reagent  for 

aldehydes . 92, 182 

Funnel,  Babo 159 

— ,  Buchner 5^52 

— ,  dropping 36 

— ,  hot  water 128 

— ,  separatory,  Squibb's 36 

— ,  — ,  globe-shaped 36 

Furfural  test,  for  pentoses 132 


Gallic  acid,  ferric  chloride  test. ...  178 

Gas  purifying  apparatus 228 

Gelatine,  precipitation  with  tannin  193 

Glass  tubing,  bending 28 

Glycine,  preparation  of 1 24 

Glycocoll,  preparation  of 124 

Grades,  laboratory 2 

Grease  for  stop-cocks 229 

Grignard's  reaction 69 

Guard  tube,  in  organic  combustions  245 

H 

Halogens,  detection  with  sodium 

decomposition 112 

Halogens,  test  for  with  "alcoholic 

potash,"  etc 38,  150 

Hardened  filter  paper 170 

Helianthine 171 

Heterocycles,  nitrogen 213 

Hexamethylenetetramine,  prepara- 
tion of 96 

Hippuric  acid,  for  glycocoll  experi- 
ment    1 24 

Historical  introduction  for  the  de- 
termination of  carbon  and  -hy- 
drogen   217 

Historical  introduction  for  the  de- 
termination of  nitrogen 269 

Hydrocarbon,  paraffin;    properties  32 

Hydrocinnamic  acid,  preparation  of  184 

Hydrogen,  determination  of 217 

— ,  in  organic  substances,  test  for.  30 

—  chloride,  preparation  of 195, 198 

Hydrolysis  of  butter 108 

ethyl  acetate 106 

hippuric  acid 124 

isobornylacetate 206 

lecithin no 

methylal 94 

Hydroxylamine  hydrochloride,  for 

preparing  an  oxime 100 

, cuprous  chloride 50 


Ink 193 

Isoborneol,  preparation  of 206 

Isobornylacetate,  preparation  of.  .    205 


GENERAL  INDEX 


329 


Ketone,  reduction  to  secondary  al- 
conoi 73 


Lactose,  oxidation  to  mucic  acid ...   134 

Lead  peroxide,  for  organic  com- 
bustions    265 

Lecithin,  from  egg-yolk no 

Liquid  crystals 67 

rf-Limonene-dihydrochloride,  prep- 
aration of 195 

List  of  apparatus  for  general  or- 
ganic chemistry 312 

List  of  apparatus  for  the  determina- 
tion of  carbon  and  hydrogen.  ...  223 

List  of  apparatus  for  the  determina- 
tion of  nitrogen 271 

List  of  chemicals  for  the  determina- 
tion of  carbon  and  hydrogen.  ...  224 

List  of  chemicals  for  the  determina- 
tion of  nitrogen 272 

List  of  chemicals  for  laboratory  ex- 
periments, "long"  course 315 

List  of  chemicals  for  laboratory  ex- 
periments, "short"  course 321 

Logarithms,  table  of 308 

M 

Magnesium  for  Grignard's  reaction  71 
Manometer,     for     distillation     in 

vacua 80 

Manometer,  for  nitrogen  combus- 
tion   281 

Melting-point,  apparatus 58 

— ,  bath  for  high  temperatures 66 

— ,  changes  in 66 

— ,  determination  of 58 

— ,  substances    for    standardizing 

thermometer 63 

— ,  Thiele  apparatus 64 

— ,  tubes  for 60 

/-Menthone,  preparation  of 99 

—  oxime,  preparation  of 100 

Mercury,  purification  of . 81 

Methane,  from  chloroform 31 

Method  of  running  blank  determi- 
nations   246 


Methylal,  hydrolysis  of 94 

Methylamine  formation  and  prop- 
erties   120 

Methylaniline,  in  test  for  2  °-amine .  1 65 

2-Methyl-butanol-2,  preparation  of  69 

Methylene  diethers,  hydrolysis  of .  .  94 
Methyl  ester  of  3.5-dinitrobenzoic 

acid 55 

—  isothiocyanate,  formation  of . . .  123 

—  mustard  oil,  formation  and  prop- 

erties    1 23 

—  orange,  preparation  of 1 70 

phenyl-carbinol,  preparation  of  73 

phenyl  ether 180 

—  salicylate,  preparation  of 191 

Michler's  ketone,  for  crystal  violet 

171,  175 
Micro-combustion,  for  carbon  and 

hydrogen 221 

Micro-combustion,  for  nitrogen. . .  270 

Mucic  acid,  preparation  of 134 

Mustard  gas,  reference 47 

N 

Nitration  of  an  aromatic  hydrocar- 
bon   154 

Nitrobenzene,  preparation  of 154 

Nitrogen,  detection  of 112 

— ,  heterocycles 213 

— ,  estimation     of,     by     absolute 

method 269 

Nitrometer 285 

"Nitronation" 155 

Note-books. ...  2 


Oil-baths 79 

— ,  water  in 82 

Oil  of  turpentine,  rectification  of .  .   200 

wintergreen,  preparation  of..   191 

Olefine  formation 40,  48,  202 

Ortho-ester,  references 94 

Oxidation  of  an  acetylene  ("  triple") 

bond 50 

Oxidation  of  a  i  °-alcohol  to  an  alde- 
hyde  54,  83,  85 

Oxidation  of  a  2°-alcohol  to  a  ke- 
tone      99 


330 


GENERAL  INDEX 


Oxidation  of  a  hydrocarbon 210 

side  chain 189 

sugar 134 

an  olefine  "double"  bond.  .44, 48 

—  with  concentrated  nitric  acid. .  .   208 

dilute  nitric  acid 134 

potassium     permanganate 

44,  48,  50 

Oxidation  with  potassium  perman- 
ganate in  neutral  solution. ...  189 

—  with  chromic  acid. 54,  83,  85,  99,  210 

Oxime  formation 100 

Oxygen,  for  the  determination  of 

carbon  and  hydrogen 225 


Palladious  chloride  solution 245 

Pentoses,  furfural  test 132 

Permanganate  oxidation  in  neutral 

solution 189 

Phenol,  preparation  of 177 

— ,  reactions  of 178 

Phenolphthalein,  formation  of.  ...   171 
Phenylglucosazone,  preparation  of.   127 
Phenylhydrazine,  for  osazone  for- 
mation    127 

— ,  for  hydrazone  formation 182 

Phenylpropionic  acid 184 

Phosphorus,  detection  of 112 

Pinene,  tests  for  "double"  bend  in.  45, 48 
— ,  purification  of,  for  ffinenehydro- 

chloride 200 

Pinenehydrochloride,     preparation 

of 198 

Polymerization  of  acetaldehyde .  .    .92 

formaldehyde 96 

Porous  tiling,  to  prevent  bumping.     19 
Potassium  hydroxide,  cutting  sticks 

of 3 

Pre-heater,  for  organic   combus- 
tion   228 

Preparations,  collection  of  liquid . .       4 

— ,  labeling i 

—  notes  on i 

Pyridine,  reactions  of 213 

Q 

Quinoline,  reactions  of 213 


Rape-seed  oil,  for  oil-bath 79 

,  water  in 82 

Reduction  of  a  halogen  derivative.  31 

—  ketone  to  a  2°-alcohol. ...  73 

an  aromatic  nitro-compound.  157 

olefine  bond 184 

—  with  sodium  amalgam  and  water  184 

—  sodium  and  alcohol 37 

tin  and  hydrochloric  acid.  . .  157 

—  zinc-copper  couple 31 

Reflux  condenser 26 

Resin  formation  of  aldehydes 92 

Resorcinol,  ferric  chloride  test 178 

— ,  for  fluorescein  formation 171 

— ,  in  test  for  formaldehyde 96 

Rubber  stoppers,  boring  holes  in .  .  40 
•-,  molded 3 


"Salting  out"  of  a  dye 175 

liquid 160 

Sandmeyer  reaction 187 

-Saponification,  see  Hydrolysis. 

Schiff  s  aldehyde  test 92, 182 

Sealed  bottles,  method  of  opening  33 

Sealing  tubes,  directions  for 117 

Separatory  funnel,  globe-shaped. . .     36 

— ,  Squibb's 36 

Silver-mirror  test  for  aldehydes. 91,  182 
Soda    lime    for   absorbing    carbon 

dioxide  in  organic  combustions  243 
Sodium  amalgam,  preparation  of .  .    184 

—  benzene  sulfonate,   preparation 

of i52 

Sodium,  "bird-shot" 141 

—  bisulfite,  reagent  for  aldehydes, 

etc 98 

Sodium  bisulfite,  preparation  of 

reagent 98 

Sodium  bisulfite,  for  removing 

stains  of  manganese  dioxide 196 

Sodium  hydroxide,  cutting  sticks  of  3 

—  residues,  treatment  of 5,  69,  143 

Starch-potassium  iodide  paper. ...   187 

Steam  distillation 158 

Stem  correction  for  thermometers.. 8,  20 


GENERAL  INDEX 


331 


Still-head 25 

Stop-cock  for  equalizing  pressures 

above  and  below  it 278 

—  grease 229 

Stop-cocks,  removing  "frozen"...       4 
Stoppers,  glass,  removing 4 

—  rubber,  boring  holes  in 40 

,  molded 3 

Suberite  ring 141 

Sublimation,  method  of 211 

Sucrose,  hydrolysis  of 127 

Suction  filtration  of  small  quanti- 
ties      56 

with  Buchner  funnel 51-2 

Sugar,  hydrolysis  of  cane 127 

Sulfanilic  acid,  preparation  of 167 

Sulfonation  of  an  aromatic  amine . .  167 

hydrocarbon 152 

Sulfur,  detection  of 112 


Table  of  atomic  weights 

Inside  back  cover 

corrections  for  barometer. . . .  300 

logarithms  and  a  n  t  i  1  o  g  a- 

rithms 308 

vapor  pressure  of  water 301 

weight  of  i  cc.  of  nitrogen  at 

different  temperatures  and 

pressures 303 

Tannic  acid 193 

Tannin,  ink 193 

— ,  reactions 193 

Thermometer,  short  scale 8 

— ,  standardization  of,  for  b.-p 7,  20 

— , m.-p 63,   64 

— ,  stem  connection 8,  20 


/>-Tolunitrile,  preparation  of 187 

/>-Tolyl  cyanide,  preparation  of . . .   187 
Topical   outline,   for   carbon  and 

hydrogen 224 

— ,  for  nitrogen 273 

Trans-i .8-dichlor-terpane,  prepara- 
tion of 195 

Triphenylmethyl,  formation  of. ...   147 
Triphenyl-methyl-peroxide 147 

U 

Urotropine,  see  Hexamethylenete- 
tramine 96 


Vacuum  desiccator 87 

—  distillation 76 

—  valve 78 

W 

Water,  vapor  pressure  of  (table).. .  301 

Weighing  liquids 267 

—  the  absorption  bottles 248 

substance  for  carbon  and  hy- 
drogen    250 

,  —  nitrogen 292 

Woulffbottle 198 


Yield,  notes  on i 

— ,  theoretical i 

— ,  practical i 


Zinc-copper  couple 31 


INTERNATIONAL  ATOMIC  WEIGHTS,  1920. 


Atomic 

Symbol,  weight. 

Aluminium Al  27.1 

Antimony Sb  120.2 

Argon A  39 . 9 

Arsenic As  74 . 96 

Barium Ba  137.37 

Bismuth Bi  208 .  o 

Boron B  10.9 

Bromine Br  79 . 92 

Cadmium Cd  112.40 

Caesium Cs  132.81 

Calcium Ca  40 . 07 

Carbon C  12. 005 

Cerium Ce  140. 25 

Chlorine Cl  35.46 

Chromium Cr  52.0 

Cobalt C  58.97 

Columbium 93 .  i 

Copper Cu  63.57 

Dysprosium Dy  162 . 5 

Erbium Er  167.7 

Europium Eu  152.0 

Fluorine F  19.0 

Gadolinium Gd  157.3 

Gallium Ga  70. i 

Germanium Ge  72.5 

Glucinum Gl  9.1 

Gold Au  197.2 

Helium He  4 .  oo 

Holmium Ho  163.5 

Hydrogen H  i .  008 

Indium In  114.8 

Iodine f I  126.92 

Iridium Ir  193 .  i 

Iron Fe  55.84 

Krypton Kr  82.92 

Lanthanum La  139 .  o 

Lead Pb  207 . 20 

Lithium Li  6 . 94 

Lutecium Lu  175  .o 

Magnesium Mg  24.32 

Manganese Mn  54.93 

Mercury ^g  200:6 

Molybdenum Mo  96 .  Q 


Symbol. 

Neodymium Nd 

Neon Ne 

Nickel Ni 

Niton  (radium 

emanation) Nt 

Nitrogen N 

Osmium Os 

Oxygen O 

Palladium Pd 

Phosphorus P 

Platinum Pt 

Potassium K 

Praseodymium Pr 

Radium Ra 

Rhodium Rh 

Rubidium Rb 

Ruthenium Ru 

Samarium Sa 

Scandium Sc 

Selenium Se 

Silicon Si 

Silver Ag 

Sodium Na 

Strontium Sr  f 

Sulfur S 

Tantalum Ta 

Tellurium Te 

Terbium Tb 

Thallium Tl 

Thorium Th 

Thulium Tm 

Tin Sn 

Titanium Ti 

Tungsten W 

Uranium U 

Vanadium ,.  V 

Xenon Xe 

Ytterbium 

(Neoytterbium) . .  Yb 

Yttrium Yt 

Zinc Zn 

Zirconiun... 1i 


Atomic 
weight. 

U4-3 

2O.  2 
58.68 

222.4 

I4.008 
190.9 

16.00 
106.7 

31-04 
iQS-2 

39.10 
140.9 
226.0 
102.9 

85-45 
101.7 

I50-4 

44.1 

79-2 

28.3 
107.88 

23.00 

87-63 
32.06 
181.5 
I27-S 
159-2 
204.0 

232.15 
1 68-.  5 
118.7 

48.1 
184.0 
238.2 

51.0 
130-2 


173-5 
89.33 
65.37 
90.0 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 
BERKELEY 

Return  to  desk  from  which  borrowed. 
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JAN    28  1948 
MAR    16  ii* 


21  OctS  [At 
70ct5ILU 

SNovSlPA 


LD  21-100m-9,'47(A5702sl6)476 


YC  21670 


THE  UNIVERSITY  OF  CALIFORNIA  UBRARY 


